Assuming the current business model is providing the Scirra team with a healthy long term, sustainable income, I don't think there is a need for change...
And change at this point would make many of the early adopters feeling pretty let down...I think many would jump ship...
Construct 2 is cheap if you use it on a regular basis and or to provide your income, but for every hobbyist and developer that could be potentially milked for a subscription fee, there is someone who bought the lifetime licence and all it provides and will only use it for a few months...
Look around the forum many of the "paid up" newcomers will have fallen by the wayside well before the year is out...