I suppose you could potentially add that to the focused review options, to peek tomorrow and maybe even "do tomorrows reviews".
I could see myself getting a quiet day and thinking "I could do tomorrows" whereas the focused reviews for me at the moment feel like I'd always be taking on too much.
The way the system is set up, if you do a review that is not ready yet, it will just review it, and not push the mastery level up, so that would have to be changed as well should this be implemented at some point.
Yeah, I think the idea of completing tomorrows reviews and it effects the algorithm needs some more thought if it's a good idea, but just peeking tomorrows review numbers I'm hoping is more simple :)
If you need just numbers, they are available separately on each schedule summary. Just tap the name of the schedule, and the daily goals for future days are listed there!