Good question -- I don't know if they talked about their plans about new javelins. I know they want to, but for now it seems the core game has been balanced around the 4 current javelins 'classes'.
Yeah, ATM I don't think even BW knows what to do about them.
My feeling is they will just clone the Warframe playbook, have a complete Jav + some exclusive cosmetics sold as a real money package; but have the components that you can use to build one yourself to drop in various missions that you will have to farm (alternatively sell the components for coin that you can farm in game).
If BW make it so one can only get the new Jav by buying with real money, there will be instantly nothing to do (or can do) for those who never intended to pay for new Jav, and those people will simply move on to other game as there will be no point sticking around. Bleeding player base like this is exactly how you kill a GaaS game.
From what I have observed via various tweets/stream/threads by the Dev, my impression is they are FULLY committed to run the title as a long term full GaaS title, and the core of all GaaS title especially online multiplayer titles are player base, player retention and washout rate mitigation.
