I think the comments about them being at fault here for not retiring are a bit twisted.
Of course they don't if you keep praising them and let them start every important game. If the coach/club wants them out tell them, bench them more often, try to build up a new starter for their position or get a new player to do so.
This shouldn't even be discussed, players shouldn't be the one deciding when they are replaced. Just do it, and if Busi or Pique want to stay longer anyway then so be it. Xavi wasn't a starter anymore when he left, Puyol had injury problems and for Iniesta we already signed Coutinho to take over. Meanwhile Busi is out there being "the best DM in the world" with basically no competition.