Here’s probably the way I’d deal with older modules:
At the 5 year mark from complete release (NOT EA release), look at what needs to be improved, remade or redone. Cost/benefit ratio applies here; if it doesn’t cost much to keep it going, then roll QOL improvements into the price for new buyers. Otherwise, start a process on creating the next iteration, make users aware that in a couple years there will be an upgrade and it will cost money.
7 year mark, new version built with new improvements rolled in, final updates to old version done. Old version will be supported for a while longer, with the new version taking priority. New buyers get new version, old buyers get option to buy new version at a discount. Both exist in the game ecosystem for a while.
10 year mark, new version takes priority, old version is deprecated; old buyers have the option to upgrade at the above deal, but will have to use older DCS World version to use their previous version. Old version no longer actively supported from this point.
Much of this depends on whether or not the module needs improvements or changes. For both the A-10C and especially the Ka-50, they’re both getting to the point where they’re old enough that they need significant changes and upgrades, which costs money. I’m personally OK with paying the price for an upgrade after a period of time, as there’s usually an advantage for doing so – A-10C with JHMCS, Ka-50 with MLWS. So as long as the upgrade cost isn’t prohibitive, it’s all good.
As noted before, my main hangup with DCS going to subscription is for those of us that have already paid into it. I preordered the F-16 and F-14, paid full price for the F/A-18 and the Persian Gulf in 2018, and have done most of my module purchases in less than 2 years. Should DCS go to a subscription model, I expect to get a few years of free use of DCS, since that’s what I’ve paid for in effect. I’m not the only one, so ED would in effect be running only on their existing funds for a huge number of existing customers.
Going to a subscription model right now would be a very bad move for ED, since their customers aren’t full of types who like that software model. However, they could potentially roll out the option to get a subscription while retaining the existing payment model. Those who have paid in still have their licenses, new buyers get the option to try before they buy and possibly buy a module they prefer over the subscription. This way, ED can figure out if a subscription model substantially helps their finances, doesn’t change much, or is just another tool in the box.
I’ll be honest: one of the key hangups I have with the subscription model is I don’t see it changing ED’s work ethic. Paying a subscription and then waiting 3 years for critical bugs and problems to be fixed wouldn’t fly for me. There seems to be this belief that throwing money at ED would fix problems, but that’s not the way the world works – never has, never will.