Yeah they should make new games to fill in the gaps in the old timeline. And if they ever need to make a new timeline, they could make one where Galamoth (or someone else) became the new Dark Lord by killing Dracula , pretty much what could have happened in Judgement if Galamoth succeded in defeating Dracula . I know that game isn't really cannon(or is it canon?) but it would make more sense to make two timelines that are somewhat connected, like an parallel universe, and not just start the series all over and stick the name Castlevania on it( what LoS did).
Also didn't Alucard say that there would always be a dark lord, whether it's Soma or someone else?So the timeline isn't finished. I'd like to have a game that takes place after Dos, which narrates the rise to power of the new dark lord.That way the old timeline will continue , maybe not forever but for a long period of time. They can always make games for the new timeline, for those who really like Los.