I think that depends on a couple other questions.
Does PHX make 12in tablets for models where the there is an OEM 12in option? They don't make one for the RAM, so pretty sure the answer is no.
Will Gen 3 have an option that doesn't come with 12in? Or will there be enough F150/Raptor owners who get the 8" screen willing to update to 12in? Hard to say, but seems unlikely.
Does PHX have enough business just focusing on older model vehicles. Seems they do.
For me personally, the question is, will there be a reason to use a PHX screen instead of an 12in OEM screen? I see two advantages to PHX. The first is that there is no screen lockouts while driving. The other is that you have access to every app in the Google store. These are features I would miss. However, an OEM screen should be much more reliable, and the most common applications should be available through android auto and carplay.