Unless you have old DS-125's it would seem to me on a quick analysis, that it would be cheaper overall to sell a DS-125 and buy a DS-160, rather than pay for the upgrade. A new 160 is about $750, and you can get about $500 for a used 125.
So, I don't see that as a downside.
It would seem the real upside in this is the ability to get old 125's up to current TTL standards. That is a HUGE upside for those with old 125's.
Certainly when the DS-160 and 161 came out they had no plans for upgrades. Likely with the requests and the poor economy, they had a change of heart. I wonder if they actually make more money, on a net basis, performing the upgrades rather than selling a new 160. Of course, we will never know.
I applaud Ikelite for the upgrade. I have had nothing but great experiences with them.