Ooooh, I can see that happening : 8+2 mopping the floor with the green MP-EVAs, then suddenly Gendo launch the command to "awake" them, all of their armor morph to a more organic one of bone white color, and their helmet then explode revealing their eyeless and perpetually grinning face, hundreds of harpies ready for battle.
SURPRISE! YOU'RE FUCKED 8+2!!!
As for EVA-13, it will definitively appears in Final, an awakened god with two superpowerful spears embedded in it, just laying here waiting to fall into the enemies' hands? Impossible!
Maybe Gendo retrieved it and will fit it with a Dumy System to fight alongside the MP-EVAs? Or maybe it's necessary for his Final impact?
If it landed not too far from EVA-08, I can't see WILLE at least trying to retrieve it, if only because it's too powerful to lay in the ruins unsupervised. Maybe we didn't saw it with 08 and 02 because WILLE put 13 in a special quarantine zone with angel sealing hex pillars. Maybe in Final they will give it to ReiQ(Kaworu said that she can't do the synchronized ATF, not that she can't pilot it) if she managed to gain their trust(that would imply a time skip), or to Shinji if the plot made it so WILLE don't have any other choice. Personally I don't see Shinji going back to piloting EVA-01 in Final : firstly that would basically mean going back to mommy for help, and that would be detrimental to Shinji's character development, secondly 01 escaping would mean putting the Wunder out of action, unless they replace it with EVA-13, but I don't see it happen because of the first point, thirdly from the little we saw of it in space and when Asuka plugged the ignition system, 01 seems to have muted into something trying to change into core material anything around it, not really a safe thing to let roaming around, and finally EVA-01 is still with the old armor or mutated into something covered in core material, not something really appealing to sell as figures right?