My take - not that big a deal.
Previously you Army guys had the (generous and surprising) option of renegotiating multiyear MSP contracts if the rates went up. For the moment I guess Navy and AF still have this option.
Eg - you're in year 2 of a 4-year contract for a total of $50K extra per year when they raise the 4-year rate to $60K/year. You could sign a new 4-year contract at the $60K rate, effective immediately. (Doing so extends your ADSO to 4 years from the current date, but you get the higher pay immediately.)
I've always thought it was odd that they allowed mid-contract renegotiation for a higher rate. Not surprised at all they put a stop to it, but it does make me wonder what the point is, unless they plan to INCREASE the rates. Which seems unlikely. The only way they lose money is if someone bails on a cheaper contract for a more expensive one.
Here are the only two hitches that prevent me from saying it's not a big deal at all:
1) It appears that people with existing MSP contracts who do fellowships will no longer be able to renegotiate the contracts to align their ADSO dates. Now they'll be stuck with the same academic year vs fiscal year BS the rest of us live with: either decline ISP from the Oct 1 - Jun 30 period of the final year of ADSO ... or take it and extend the ADSO until Sep 30 of that year.
I'm not sure this is really that big a deal, as people taking MSP tend to be lifers anyway, so an extra 3 months might not carry the same sting as for the guy who's getting out ASAP.
2) Say you have 7 years until retirement.
Under the old circumstances, you could sign a 4-year contract for the maximum pay, then at year 3, 'renegotiate' another 4-year contract, even if the rates hadn't gone up. That way, you'd get the maximum 4-year rate the entire 7 years.
Now, you'd have to finish out the 4-year contract, then sign a 3-year contract at the lower 3-year rate. (Or sign a 2nd 4-year contract and stay an extra year.)
My MSP eligibility years number 8, so I'm luckily not affected by that, but it will surely affect some.
Edit - thanks J-Rad for posting the PDF.