Any established developer would keep their own backups of their setups. If they only have one copy on one hard drive, I would say that such a developer isn’t very serious, or does not have a lot of experience and might as well go VST3. >
Sure, and Steinberg is also an established SDK developer, so I think they should also keep a backup copy for their clients 
. On the other hand, not all developers are established developers, hundreds of vst developers are just single programmers working in spare time from home to do a vst or two. I believe Steinberg supports all, not just ESTABLISHED developers.
Even an established developer can possibly have a disasterus situation where a whole building burns or some thing like that. No backup will help you here unless its stored at homes or some where else.
There has been many discussion with various reasons why many developers have not moved to VST3 and I would say that the most piercing reasons are that “VST 2.4 could’ve been tweaked to accommodate most VST3 features”, that “there are not enough hosts supporting VST3” or that “there isn’t enough demand for VST3”. If we always follow this trail, we would never get anything new. Be happy that Steinberg has platinum balls to do these things!
The idea is simple. I think it’s fundamentally wrong to pull a critical piece of software such as an SDK just to let the flow move to the next level. Provide enough reason for the flow to move up and they will surly gradually move. Developers are not naive, if they feel Strindberg is forcing (allthough it’s not) they will think so.
As far as all those other examples of keeping the past, how do look at Microsoft’s Windows RT?
(I would say that they are in the same league as Steinberg in terms of sizable cojones.)
As far as I know, Windows RT does not throw the Win32 API away. Win32 API is at the core of Windows libraries, without it no program will work, including VST3 or VST2. It’s solid rock into the heart of Windows. Microsoft occasionally adds new functions to it, or declares a few old functions as obsolete while still keeping them, BUT NOT totally remove it. Thats what you do with an SDK, it’s not an ordinary piece of software, too much depends on it.
Correct me if I’m wrong.