Personnally, if you're increasing the page size, then a change from 2k to 4k isn't much of a change.
I've experimented and found (in my experience) that the best size will be dependent on your SAN or disk - but 8k, 16k or 32k would be better.
On some EMC SAN I found 16k pages optimal, and on others 32k pages were optimal.
Check the page size of your disk/SAN and either make it the same size as that or half the size.
Some might say that having larger pages will increase locking on allpages tables. Whilst that sounds true in theory, in practice I didn't notice anything. A physical page read is about 1000x slower than a memory page read - so if you're doing disk reads -you really want them to be quick and get as much data as fast as you can.
We went from 2k pages to 16k pages and possibly we should have gone for 32k pages (which is the page size of the SAN).
Yes - to load a 2k dump you'll need a 2k server. Its not great - but perhaps a VM could help here
We're not fully on Sybase 16 yet - but can't see much change (apart from a few new features) from 15.7. But its early days.
If you're coming from 15.5 then we found these issues (as part of going to 15.7)
It has the threading model - which (in my experience) needs some configuration experimentation to get right .
It also needs a lot more procedure cache (and I mean a LOT more) - this really hurt us. See the postings on this - Simons traceflag setting really saved us!!