Does anyone know if the spring and follower are available or going to be made available instead of buying new magazines?

Frankly, if two rounds make a difference (15 vs 17),there's a whole bunch of WTF happening for you.

30-round VP9/P30 mags

Run the 15s, and use the big boys for HD or when you're someplace hunkered down.

To answer your question OP, I haven’t heard of them doing that yet. I’m sure the new parts will come in eventually, but it may be a while before supply catches up with demand. I know I have a bunch of mags I wouldn’t mind upgrading.

No one has heard for certain that I have read about.  I would imagine the parts would be available at some point but you know everything will go to new production for the near future.  I would guess the aftermarket would probably step up and copy the 17 round follower before HK gets around to selling mag parts.  You can always get some Xtech Tactical mags.  David

If you are looking for new 17rd mags, Aim Surplus has them for $39.95 in their weekly email today.

I sold all my 15 round mags for like $38 locally and bought all new 17 rounders for just under $33 per mag.

Where did you find 17rd mags for $33 each?

Lanbos Armory has them for $33

A local dealer sells em for cost to LEO.

does the new magazine follow the Glock and Mecgar model of removing all space for the spring and compress the hell out of it when fully loaded?  Also removing any give when fully loaded and making it difficult to insert a fully loaded mag on a closed slide?

If you compare old school Sig and Beretta mags to their new counterparts that often hold +2 more rounds, you will see the follower leg has been eliminated or even hollowed out.  Usually resulting in the mag spring being compressed to an inch of its life.

Now granted, I haven't seen too many of these springs go to failure, but have seen the follower seems less stable in its stack.   They are definitely harded to insert when fully loaded compared to their old school brethren.