I also do feel guyot will be the last enemy in the series, however i think guyot will first first be processed to become a second class zoalord first, maybe by obtaining one of the zoa crystals from one of the rogue zoalords after he dies off by the hands of apollon but somehow is not able to retrieve the zoacrystal (maybe too many enemies prevent him from doing so).
I do not believe alkampfer will be able to gain a g unit but he will reach back to his own old self in terms of power, probably through a sacrifice of murakami.
Somehow Alky gets put is a tough spot by taking a giga smasher in the face together with facing exceed and has to come up with a on the spot alliance with Guyot who now holds the power of the incomplete g2-f unit, but in the middle of the fight he manages to betray alky and get hold of guyver 3s g unit plus gigantic.
Then a final fight happens between exceed and guyot while everyone else is having tea in the happy neighbourhood and aptom marries fumiko. I might be wrong about the last part.