I can't wait for people to find out that the new MBP has the same old 4 TB3 ports as before - especially the guy that was given the
3 TB ports+HDMI+SD+Magsafe version of the fake schematics made to flush out the leaker...

(NB:
joking, please don't waste time arguing about that suggestion!)
But let's just assume we can trust the rumours:
Last I looked, "MagSafe"
was "a proprietary magnetic connector power cable". I don't think anybody will be surprised if any new MBP MagSafe isn't compatible with the old MagSafe 2 connectors, though.
The iMac version pretty obviously isn't intended to be "safe" against being pulled - but then that wouldn't make sense on a desktop which (a) was mostly going to be used with the power cord safely tucked behind a desk and (b) doesn't have a battery so will crash and loose all of your work if the power gets disconnected. The magnet on the iMac seems to be there for thinness and to supply > 100W (the TB limit).
Apart from the breakaway "safe" bit, the only other reasons for bringing MagSafe back to the MBP I can think of are (a) freeing up a TB port from power-supply duties (if they are cutting one) and (b) if they need more than the 100W power provided by TB... but then a 240W version of USB power delivery has just been announced, which won't be a surprise for Apple so not making it "safe" defeats at least part of the whole point...
Remote possibility is that it will be a complete TB3/4 implementation in magnetic form. Not holding breath.