I don't think you'll see 16 team playoff - but 8 seems likely at some point. 8 games means you reduce many teams by a game, 16 maybe reducing two in the regular season.
That is a ton of stadium and regular season tv revenue that the extra playoff games would need to recover. Take Penn State, Alabama, Nebraska, Oklahoma, Michigan and other teams that draw consistently 90-100k fans. A game represents $5mm plus in revenue (as an example, with pro-rated seat licenses, EACH home game at Nebraska is worth over $8 million in ticket/seat revenue this year). Throw in $35 million in tv rights this year (not including bowls) and there is motivation to not expand playoffs too far.
If/when they move to 8 teams, that means two teams would play 16 games (12 reg season, one conf champ, three playoff games). If they could make the first round of the playoffs the conference championships to fill six spots and have two at large, a case could be made for one more power conference - but would the P5 let that happen? Why wouldn't they demand 5 spots, open fill the other three to include at least one non P5 team? That seems to be the way they roll.
IMO, if the Big 12 came calling, that is the shortest UCF route to P5. Their need for a playoff game is big enough that something is going to happen there or they run the risk of dissolving with a UT and/or OU leaving. If the Big 12 dissolved - then cue up AAC or a reconstructed Big 12 combo platter with UCF. UCF can make itself an attractive addition - especially located in Florida with a huge student/alumni potential.
Of course none of this will be right, something mooky will happen and all the seats will rearrange some how next year....