The exact wording was:
"The most important thing for Thiago is that he keeps on getting games. I think he'd get them at Barça."
I'm assuming the context was in regards to where Thiago stands with the national team and the world cup. The direct implication of this quote is that staying at Barca won't hurt his chances. In other words leaving to get a better chance with La Roja is no longer a valid reason for leaving. That leaves money and club appearances as the possible reasons.
There's hearsay that Tito plans on giving Xavi significantly less minutes next season. Those minutes would most certainly go to Thiago if he stays.
That's not guaranteed, it's also possible that Cesc would get extra minutes. I would say the key factor in Thiago getting more minutes next season is him staying injury free.