@JeremyECrawford ok, interesting conundrum. I've got a high level wizard on the verge of being able to cast wish. If I were to wish to turn myself into a dragon, could I keep my wizard levels?
— Will Ivancic Aether^ (@AetherSpike) April 23, 2018
The description of the wish spell lists the things you can do with the spell reliably. If you try to do something—such as permanently becoming a dragon—that isn't on that list, the DM determines what happens, based on how you worded the wish and on other relevant factors. #DnD https://t.co/TrPF8JyElG
— Jeremy Crawford (@JeremyECrawford) April 23, 2018
Not an expert but if I was the DM and a player wished to do that I would have them change their wizard levels for Sorcerer – dragonbloodline – the color dragon they became (if they didnt say what color I would randomly roll) of an equal level as to what they were when they cast the spell. (and yes that would also mean the +1 to hp for each level that the bloodline gives)