I am very happy that UE4 is free for now. But do you think think they will bring back subscription model when they need money like in future?
I dont think that this will be the case -> especially in the future they will get pretty much money from all the published games 
only the future knows but its unlikely, the market place and royalties will likely be the fuel for this epic train
but if they did im positive many would be fine with this after all they have done for the developer community
Many people have already paid a license for the engine which allows you to use the engine indefinitely so, if they were to bring back subscription, unless they allowed all prior owners to continue using it then they would be kind of violating their own terms for the engine.
They earn money off finished projects anyway so that’s a form of payment, and also the stuff available on the marketplace is another source.
So far Epic has shown they DO know how to please the crowd. I doubt they’ll hurt their own reputation by doing that.
Epic isn’t going to be needing funding desperately anytime fast IMO. They run a good business, plus they have the backing of TENCENT, one of the largest internet companies in the world.