I'd imagine they would both stick with 7nm since the yields by next year should be acceptable in time for production for the holidays. If one company was going to shoot for 7nm+ I think it would be MS. They are likely to sell less consoles in general, especially if they come out with a higher performing more expensive console, so they could deal with lower yields and not worry as much about cost, even if it meant absorbing a little more early on. This would be what MS would need to guarantee they end up with the strongest console head to head next holiday, if both are looking to sell for around $499. Scarlett either wouldn't be all that much more powerful, or would be, though more heavily subsidized. Now if PS5 was around 8TF, and Scarlett ended up around 12TF, then you can almost bet that PS will keep PS5 $100 cheaper than Scarlett, so is that worth it for MS in terms of marketing? I would guess that MS would rather use 7nm and just make the cooling beefier and console larger if they need to instead, which should help it remain more cost competitive on the shelf.
If MS doesn't at least double the TF number for Scarlett it will look bad on them. If they don't focus on it, or use another indicator like Navi or how many CU's it has and not the TF, that's going to look even worse. I mean MS is already using terms like custom Scorpio Engine processor for XB1X, making sure not to mention Jaguar. PS can use whatever direct terminology for PS5 and it's not really going to matter for them, even if the TF count is lower than Scarlett. Pro was 42% less powerful on paper than XB1X and it really didn't impact them. New gen or not, with BC in the mix plus the PS4 brother's staying relevant and tied to PS5, marketing for Scarlett is going to be tough in terms of hardware.
If Microsoft able jump to 7nm+ than there is no reason Sony cannot, because actually 7nm + is more cheaper for the long run for both company and both are releasing at the same time frame (unlike Xbox One X that release latter after PS4 pro). Because i also have hunch both will targeted 7nm + due to release date and several news that 7nm+ already available on Samsung this month for mass produce and TSMC will be available late this year or early next year.
The problem is the devkit and the test chip for the 7nm+ APU, they need to get at least 1 year or 6 month prior to launch, and none of manufacturing company able to produce in early 2019. That is why many forum dweller are pessimist that Sony and Xbox are using just normal 7 nm for devkit and for the final design.
For the price i think both will targeted at the same price and Sony also willing to subsidize more this time (they are focusing next gen on hardcore gaming is the prove for this) So we will see both ended up the same spec and the same price.