when was the last ipad pro released,
I want one , buy now or wait until next release ?
They were announced 30 October 2018.
Only you can decide if you should buy one now or wait. Do the ones that are out now meet your needs? Is it important that you have one now (e.g. you need it for work or school right now)? Do you have the money? If the answer to those questions is yes, you should buy one.
On the other hand, if the current ones don't meet your needs, you shouldn't buy now.