If there's a sequel---
It'll be really hard to find an enemy that is more stronger than Anti-Spiral, a crisis that is more dangerous than Spiral Nemesis, and also-- a mecha that can surpass the size of Chou Tengen Toppa Gurren Lagann.
Gurren Lagann legacy is started through Simon, it also ended through Simon itself.
If there's a sequel, somehow I doubt if there's a chance to defeat or even creating a will that'll be able to defeat Simon's will.