This reminds me of the discussions back in the days before Sonar was made VST compatible.
There were some quite valid reasons as to why Cakewalk wouldn't support VST when it was such a de facto standard - including the fact the DX was supposedly
superior in many aspects and offered better possibilities. Ron Kuper had some pretty good arguments and promising ideas.
Eventually, we finally saw a few major manufacturers supporting DXi, but eventually, Cakewalk gave up on fighting that uphill battle and implemented VST.
10 years later, we're back to square one, more or less. No matter how many arguments against VST 3 can be made, no matter if 2,4 could have allowed much of what's in 3. VST3 is here.
I somehow doubt that Steinberg gave a discount to its former employees to implement VST3 in Studio One - yet, it was implemented. As such, I have no idea what makes it so hard and expensive to implement in Sonar.
Technically, Sonar can probably do pretty much everything w/ VST 2.4. And it's good to know that VST3 is in the pipes. But I don't think adopting VST3 in X2 would have hurt.