Over the last couple of weeks, there have been hints that the match between Roman Reigns and Brock Lesnar will be a title vs. title match. Brock Lesnar has stated in his promos that he wants both belts on the line. Lesnar lost the WWE Championship to Bobby Lashley at the Royal Rumble due to interference from Reigns.
Dave Meltzer stated in the Wrestling Observer Newsletter that the original plan was for a title vs. title match not to happen but plans change so frequently but the idea is to book Reigns and Lesnar as strong as possible because the idea is that this is the biggest match of the year and that they are well above everyone else and their match is considered a dream match.
Lesnar will be in the Elimination Chamber match and since there are no disqualifications and count outs in that match, they are limited in what they can do if they don't plan on having Lesnar win. However, Meltzer stated in the Wrestling Observer Newsletter that the feeling in creative is that Vince McMahon will go with the call to go with the title vs. title match, which means that Lesnar would win the Chamber match.
It was also noted that people in the company stated that Heyman and Lesnar have been pushing for the title vs. title match. Meltzer added that as of now, the course to WrestleMania is set for both titles and there are lots of twists and turns to come with things playing out at Elimination Chamber.
Given that Lesnar has been talking about "title vs. title" on TV, it seems likely that this is the direction they are going in.