This is culled from public information.
Bungie made a 10 year commitment to developing Destiny. Destiny 1 was in development for 5?+ years.
You shouldn't approach the game with the mentality of other products. It's not a get on the shelf and forget about it except for DLC. This is a service. An ongoing service that you're not paying a subscription to (You can play Destiny without a Live/PSN+, you just won't be able to do multiplayer stuff). Destiny characters exist across the same brands, you can play your MS character on 360 and Xbox One. If you purchased Destiny Digitally, you can upgrade your copy to Next Gen for FREE. The upgrading is unheard of. This should be evidence of the commitment. It's not going to be 4 years later and "oh shit, you need to reroll all new characters".
Analogy time:
If you get any other console game, you're getting a completed model of a house that has pre-planned expansions.
Destiny is like getting a lego kit. Yeah there's instructions on how to make what's on the box, but everything in that box can be configured for something else.
The train didn't "stop" the day Destiny 1 shipped. I can't talk at all about what's down the road but you can use your imagination. I'm rolling classes in Destiny 1 that I'll want to play 2 years from now. If you went to college for 5 years and your Freshman-Senior year work was published when you graduated....it's the work after you graduated is what you really want people to see.
You need to forget everything else you've played before. You can't compare Destiny to any other game, if you keep trying to do that and fit a square into a round hole, you're going to have a bad time. Once you start playing Destiny for Destiny, that's when you won't be able to stop playing it.
Just pound a bunch of shots and play Destiny.