It depends on how long you can wait and the expected launch date of the upcoming phone of your choice. If the launch date is near, it’s suggested to wait for it as it’s always good to have the latest model considering latest features and launch offers. However, if the launch date is more than 4-5months, you should go for the closest matching available phone. For premium brands like Apple, OnePlus you can be sure that they’ll come up with one new model each year. As far as other brands are concerned, a few announce the launch dates in advance, so you can plan accordingly.