Yeah for sure the field will be smaller but that'll likely start to happen by next month, once a bunch of people don't make the fall debates they are likely toast. Right now only 9 are in and I can't believe Klobuchar is one of them, she should be gone yesterday. Really the only ones that should stay in from this point on are Biden, Warren, Sanders, Yang, Gabbard and either Harris or Booker.
I say that because Biden is the old school moderatel Dem, Harris and Booker are both the corporate friendly moderates who pretend to be more progressive than they are, Warren and Sanders are very close on most issues but are still individually popular, Yang while not polling as well as the others on the list is offering something very different than the rest of the pack as is Gabbard to a degree and they should both be heard. None of the other moderates are going to beat out Biden unless he continues with his brain farts and people lose all confidence in him (which there is still time for) and none of the other progressives are going to beat out Warren and Sanders.
I don't think Sanders and Warren will both stay in when the primaries come around IF Biden is still leading the pack in polls, I think they are smart enough to know that one of them dropping out gives their mostly shared agenda a better chance of being executed, hopefully ego doesn't stand in the way of progress there.