Block III will be able to operate PL-15E, that's a given and is confirmed.
3x MFDs is fine for Block III; if anything the original JF-17 MFD configuration and design was actually fairly competitive and future proof.
Aircraft like J-10B/C and F-16V have a similar configuration for their cockpit displays (the almost identical same in the case of J-10B/C), and carrying over the same future proof cockpit design helps to reduce development time and reduce need for more testing.
They have quite a bit of screen real estate to work with already, so changing to a single wide screen isn't that important.
More important are the upgrades in mission computers and processing which I'm sure the Block III will be much more capable than Blocks I/II in.
Any one have any idea on the mission computer upgrades? The videos of the original JF17A's cockpit looked laggy when they were originally shown. You are right, maybe they have fixed those issues in Block III..