Birch Plywood

what will happen if you paint oils over birch plywood without putting down gesso first?

I started a painting a piece without gesso-ing it first.
I have never done this before and am worried how it will effect the piece in 5 10 15 plus years. ths is something I am selling in a big show..

The painting should be ok for many years. The only thing that you should worry about is that when the plywood dries it will shrink and separate. It might leave gaps in your painting. If you ever decide to paint on wood the wood should be aged and fully dry. The oil in the paint should not damage the wood like it wood canvas because of the higher chemical consistency of the wood. Any changes with that will take hundreds of years.
Another thing you should be worried when painting on wood is that the wood contract and expand differently with humidity and temperature than oil paint, so you might see some flaking in the future like 50 years or so.
Paintings of Monet that were done on wood lots of them without a primer are still in good condition and there is practically no change to it.

RadBox of Birch Plywood and Anigris Hardwood