Forget the battery power, go straight to Hydrogen.

Sounds like a move to closer align to F1. It's possibly the only way to get a shake up of the super license points to try and get some US kids on the F1 radar and make Indycar more appealing to ex F1 drivers. Just a thought on why the big push.

Given that Hybrid is just a bunch of stopgap bandaid gadgets to try and minimise the inherent losses of an IC, I agree on it being nice if they dropped hybrid. I'd like to see F1 do the same, for that matter.
A much more obvious choice would be to use a type of engine that does not have those losses in the first place, and that's why you suggest hydrogen.
But I say: Indy is already running alcohol, all they have to do is assure they produce that sustainably, which, given how the quantities that motorsports uses compares to what america's roadgoing vehicles would use, is peanuts.
Same in F1: They pat themselves on the chest for going to use sustainable fuels. Unfortunately though, it's of the wrong type. In F1 too, alcohol would do just fine, sustainably wise.
And when the fuel is sustainable and -relatively- abundant, it doesn't matter that much if you bring back the 3.5 ltr V8's or any such, and consume a bit more. Now that would enhance the show again! And bring back the sports aspect of it all.
Where it went wrong, is when they decided F1 -as apparently has Indy- should be road relevant. That is about the biggest hoax imaginable actually, but it suits the commercial guys just fine suggesting that their road car is full of F1 technology, where in fact, none of them are. Commerce over sports, nothing else.

er "not only simpler"

Agreed. Pushing towards carbon neutral fuel is not simpler, tech&budget wise, for the cars themselves, but is also a more interesting counterpoint to hybrid/F1.

They are already on ethanol (although not neutral), and used to be methanol, so playing their cards on the fuel regime would fit IndyCar nicely.

Thanks for that, the engines effectively being heavily subsidized by Honda and Chevrolet was something I've somehow managed to avoid hearing about for years! That does explain some of the posturing/statements; a move to hybrid PUs is a good chance to renegotiate some deals, and as you note, put some pressure on Indycar to find more suppliers.

MichaelN, the parties that were pushing for the introduction of hybrid power units were Honda and Chevrolet.

It should also be noted that the above article doesn't accurately reflect the actual concerns that Honda has about IndyCar's engine programme and wrongly implies that the problem is with hybrid engines specifically.

On the contrary, ever since the DW12 was introduced back in 2012, they have had persistent financial problems with the cost of producing the current non-hybrid engines. From the very start, IndyCar has imposed leasing terms on the engine manufacturers that were intentionally set significantly below the cost of production, which means that the engine manufacturers have been operating at a heavy loss for more than a decade now.

According to an article produced by Marshall Pruett last year, the average cost for a team to lease engines from either Honda or Chevrolet is $1.3 million per annum for five engines. However, as a single engine actually costs around $2 million a year to operate, every single current engine lease contract results in a net loss to either Honda or Chevrolet of nearly $9 million a year.

When you look at what Honda actually said in their original statement, the complaint they raised is the same complaint that Honda and Chevrolet have been raising for the past decade - namely, they want IndyCar to find a third manufacturer to enter the series to take on some of the engine leases, therefore allowing Honda to shift some of the financial burden for subsidising the engines onto somebody else.

In fact, they don't really mention hybrid engines that much, because most of their complaints actually related to the current engine lease system - which is largely independent of whether the engine is or isn't a hybrid unit.

Nothing new, really. Changing engine type midseason already struck me as odd, if not unlikely.
Will that new engine simply be a replacement for the old engine and 'bolt onto' the old chassis in exactly the same way as the old engine? That's hard to believe, as that almost certainly disrupts the weight distribution of the cars.
The reason for postponement is not made clear, though I still stand by what I said then:
Whether it’s about overall weight, the weight distribution, dimensions, reliability or power output?
I also mentioned powers against hybrid in the first place could be at work. Honda threatening to withdraw certainly falls within that category. These hybrids are a joint venture between Honda and Chevrolet though, so maybe GM too is stepping on the brakes? So dependent on Honda they can't do it on their own?

Anyway, this comment ends just like the previous one:
This is all giving me more questions than answers.

I would guess reliability is a problem. Announcing post Indy 500 means reliable is a problem over x miles and x is less than 500.