Hey guys. I was looking through some of the blog posts and noticed there wasn't one for a plot ending. So here's my take on how SBT might have ended if the show continued. (I'll only be discussing the main story line since individual episode ideas are completely up for imagination).
Since the last episode was titled "A New Beginning" it's likely the show would have gone on for another season at the very least. Excluding the daily "monster invades Sherman," the writers however would have needed to tie up the main storyline with some sort of return to Galaluna. But before I get to that, there are still unresolved sub-plots on Earth.
My guess is that since SBT is Tartakovsky's parody on "high school drama," the love plots would have likely continued. For example, Lance and Kristin might have tried being together (this depends on how long the show would have gone on though) as well as Ilana and Jason dating. However, it won't work out for either pair, and Lance and Ilana end up together in the very end. (I'll come back to this).
The main love-line between Octus and Kimmy is where it gets interesting, as it would have had to end in some way. Before the trio leave Earth, Octus would have had to either 1) explained to Kimmy he is a robot, or 2) continue pretending to be human. If it was latter, then Octus would have broken up with her, but it would make for an awkward situtaiton. However, I don't think this is the case. Number 1 seems more likely since the show seems to hint with Lance and Ilana constantly bringing up the "robot-human incompatability" issue. My take is that Octus explains to Kimmy (and she alone) that the trio are aliens. Which is why they act strange and do everything together. He also explains that they are Titan and have to return home to fight. Kimmy accepts Octus for who/what he is and the plot resolves (probably with a prom-themed episode).
Now on to the main story: Solomon's boss ends up being Lance's father (this is assumed by many fans) and is somehow reunited with Lance after the Mutraddi send another beast. With the help of G3, the trio assemble an army and prepare to head back to Galaluna reversing the rift-gate portal. My guess is that the third/ fourth to last episode would involve this and some sort of high school graduation; again, Octus and Kimmy split and the sub plots resolve.
The second to last episode (titled "Return to Galaluna") involves the G3-trio army arriving home and engaging in combat with the Mutraddi forces. At this point anything is possible: Ilana gets captured, Lance gets injured trying to protect her, Solomon dies in combat, Lance's father makes some sacrifice to protect them, etc... Likely, Titan is formed and the tides are turned. (Seeing how the battle against the HMER was broken into two episodes, the ending battle will probably do the same.)
The final episode (possibly titled "Heart, Body and Mind") includes the Mutraddi getting defeated. Lance takes on Xeexi and the King defeats Modula. Order is restored: the Princess (Ilana) reunites with her father and Edward (Lance's dad) is finally back home. However, my personal take is that Ilana becomes queen and ruler of Galaluna. This might involve her father dying or passing on the throne. Lance is awarded for his efforts and appointed head commander of the army. Lance and Ilana at some point in the battle develop an emotional bond (some blog posts already suggest them being together), and the two enter a relationship.
As for Octus, I have a feeling that he returns to Earth and stays with Kimmy. I don't know why, but it seems like the writers would have somehow continued on despite a need to break them apart so the trio could return home...
The final scene is a fade shot of the three moons as Titan flys up into the night sky.
So, what do you guys think? I'd love to hear your personal takes on how the story would have ended.