Yeah, I got the notice via snail mail yesterday. Went online and got the same info you're presenting here...had much the same reaction, too. I'm actually glad the "closed" funds are a bit less closed, but I think they should have set the bar to get in at least a little bit higher...$250k seems low. Vanguard requires $1 million. Fido won't let you in, period. Will folks rush to get into long-closed PRWCX, in particular? We'll see.
My guess about this whole Summit thing: TRP is trying to make nice with its current investors to stem the possibility of outflows due to a variety of issues, including (1) their corporate split (and the confusion this may have caused), (2) the trend toward CITs vs mutual funds for 401(k) and similar retirement plans (M* just ran an article on that), and perhaps (3) TRP's failure to upgrade and promote the brokerage side of their biz (they NEVER participate in brokerage platform comparisons, and the few people who've talked about the online platform aren't exactly effusive with praise...plus, I've been with them 2 decades and can't recall even an invitation to LOOK at their brokerage side...always been mutual funds only).
That said, I may...MAY, I emphasize...consider getting into PRNHX and OTCFX in my taxable investments there. It could satisfy my desire to expand mid and small cap exposure over on the taxable side of the ledger (I have plenty of PRNHX in my IRA), as I talked about in my post re SMID funds a short while back.
Another possible motivation: Other places (even TIAA) are reducing their ERs. TRP bar of 1 million for institutional shares is a little steep. So, they are effectively reducing their ERs indirectly by reducing the bar.
I would have been happier if TRP opened a closed fund with an investment of $250K and over in the fund. (There was a comment that the funds can accommodate larger AUM better when TRP splits, though).
A clarification from TRP: Suppose you have over 1/2 million investment directly with TRP (or some other way allowed by TRP). Then, you need to invest more than $50000 in a fund per registration to be eligible for an institutional class of the fund. For example, if you have more than $50000 invested in PRWCX in a rollover account but have less than $50000 invested in PRWCX in a Roth account, only the former qualifies for an institutional class. TRP will very likely provide a way to do the conversion to institutional class online but until then, you need to call in for a conversion.