It's called "perceived obsolescence".
Yes, it's a real thing. If you're seeking the "improvements" made to speaker technology in the last 5-6 years, then yes - you are best to wait. No need to be impatient. You already have a great sounding speaker in the 13A.
[NOTE though, I'd challenge any meaningful improvement in the last 5-6 years, or even the last 15-16 years; speaker technology has been pretty stable. Despite the never-ending onslaught of new models, the sound quality at today's audio shows is not really any better than it was even 20-30 years ago, really......is it?]
Most importantly though: The release of a new model has the propensity to make the existing line drop significantly in value, overnight - who wants their new asset to drop in value unnecessarily quickly? So be patient would be my advice.