I think this is a good approach. However, I find it strongly misaligns with the 60 day time-limited upgrade option, where users are being asked to upgrade in good faith/people are being pushed into FOMO. I would have gladly paid a little more for the upgrade to make the economics work and not have the time limit. (Or, if necessary, an early bird $15-20, but with a later option to upgrade for $25-35). This is purely anecdotal of course, but I have not once re-bought an add-on at full price/higher price that had a time-limited upgrade offer nor do I know anyone that has.
Anyway, I've said my piece on this. That said, I'm personally very happy with my $15 purchase for the compatibility update and feel like you guys did a good job managing expectations for the update with a lot of patient explaining on here beforehand, and so I don't doubt good intentions for bringing more updates to the plane. I've had the MU-2 for close to 10 years, and the fact that I can still fly that plane today says a lot and does not apply to a lot of devs.
At the same time, I am hoping for more for the IXEG. But I'm sure us users and you devs feel the same about that one.