Button's future has been the centre of speculation for the last two seasons, with the 2009 world champion only having his seat confirmed for this year in December 2014. At the time, the majority of McLaren's management wanted to retain Kevin Magnussen, but eventually opted to stick with Button's experience alongside the incoming Alonso.
While Alonso is on a three-year deal, there is only an option on Button's contract for next season and McLaren has Magnussen and GP2 leader Stoffel Vandoorne waiting in the wings.
Despite the numerous options available to the team, Boullier says the plan is for Button to stay and for McLaren to find the younger drivers seats elsewhere on the F1 grid.
"Obviously we expect the four of them to race," Boullier said. "As far as we are concerned, at McLaren we have only two cars, so there will be only two race seats. We have two world champions today and we do intend to keep them, so far.
"Nevertheless it’s a luxury problem to have four good drivers and we will do obviously… Kevin and Stoffel are very good drivers, both of them we expect to race Formula One but if we can’t fit or accommodate them at home we will do our best to make sure they can race next year."