It seems that at the beginning, hints were dropped that Mei would get a lot spotlight second to Geki. Let's look at it, they're both the only ones who are not Knight (Geki is Prince, Mei is Princess). Aside of that, we have very little information of Goushi, Dan and Boi's tribes, but the Risha Tribe has quite some lore (such as the Golden Arrow and the life force), second biggest after Yamato. Plus let's look at it, Geki and Mei seemed to get along very well and with all those in hand, probably aside of the children episodes, we might see more of Geki-Mei, and they might be a couple or sorts...
Until Burai came along, proved to be an Ensemble Dark Horse and the attention goes to him.
Not that it's a bad thing (Burai is awesome). But perhaps the show would get much more Geki-Mei teases if Burai didn't prove to be so phenomenal. (Also if you note, which Guardian Beasts are excluded in Gouryuujin? Tyrannosaurus and Pteranodon)
Although Kai wasn't exactly a paragon of virtue when he was alive, Bandora seemed surprised by his aversion to being touched after being resurrected, along with his claim that he was now Satan's child. Add to that his strangely subdued emotions until Satan is killed, along with his deathly pallor, and it seems likely that Kai was a puppet of Satan's. Perhaps he only regained some semblance of his past self as he was dying, when he cried out for his mother again, seeming more emotional for the first time...
The rangers didn't really go to heaven.
Goushi shows up in Gokaiger. Geki shows up in the Kyoryuger / Go Busters
crossover. And besides, not long before the end, there's episode #46 where Mei tells the woman how she hopes to come and celebrate the old lady's birthday year after year. Is that something you would say if you plan on going to heaven as soon as you defeat the villain?