I don't think any large reptile can really be the next big thing. The problem with big reptiles is that they demand an awful lot as far as husbandry goes. Even iguanas - who now come in some way cool colors and have probably the easiest details of any reptile - need way too much space and specialized care to be widely popular (custom cages and expensive lighting from top to bottom). Not to mention big poops are a major turn off for a lot of people.

Small reptiles like corns, balls, beardies, blueys, and leos dominate the pet trade because pet stores stock everything you need for them with few exceptions. Maybe frilles will but their heads into the "it" crowd, but then you have to factor in temperament. A rowdy reptile won't be popular in the trade either.