If there will be a new iPad Pro than I can buy the 2017 version too?

Not necessarily

Let’s say there’ s a press conference in early november announcing a new iPad model. they will give a release date and on that date the new model will be for sale. The previous models will likley go on sale to deplete their stock and for a few months both old and new will be sold side by side.

then again, they may announce nothing and the models for sale now may still be sold until further notice.

You can buy whatever you want.

There may or may not be a new version of the ipad pro - there will probably be a press conf in oct or nov if there is to be anything released for the holidays.

If a new model replaces an existing one there is usually a few weeks where the models overlap and are both available.