There are a couple guys on xda citing 'inside sources' that ICS development is underway at Motorola right now. They've been right before, but I too take that with a grain of salt.
However, silence <> no ICS.
And Yes, Tegra 2 vs. OMAP is a big deal...Nvidia has to figure out what they need to do to their HAL layer to support the calls from ICS for the OMAP HAL layer. That takes time to research, develop, test, and distribute so that Moto can start building ICS around their phones. (And, Nvidia may have already done that.)
I am also hoping for a Moto official release as I do want the webtop, car mode, kickstand mode to all work with ICS. But...that all takes time!
It isn't just some setup.exe and ICS starts running...there's considerable effort & expense that has to occur. Moto's blog said they wanted to get ICS on as many of their phones as possible...I take that as a very good sign.
AND...maybe most importantly...Sprint has to also want ICS on the Photon. Which means Sprint's apps bloatware likely being developed, tested & installed, as well as all the carrier testing Sprint would likely do before distributing ICS out to us.
Add all that up and ICS has to go through a lot of changes/development/testing before we'll ever see it. It isn't just Motorola's decision...so let's not forget that.
I'm cautiously optimistic, but I'm willing to wait for it to make sure it works right the first time too.