Nothing, you shouldn't invest one penny in a bike you already own if you are going to buy a complete brand new bike. If you were building something up from parts, then that would be different. But, you are going to buy a bike that will have components on it that you could spend a hundred bucks or more on very quickly right now.

I gotta say though, there are much better flatland complete bikes than the M6. Haro doesn't build a flatland bike right now. They build a street bike then try to make it into a flatland bike. The completes on flatlandfuel are much more value for your money and have a higher grade of components, geometry, and style for your hard earned cash.