When will the BMW F15 model change?

It will not 'change'. That would imply that they keep the F15 model generation but somehow amend (or indeed 'change') it, as in a facelift etc. Instead, BMW have already said that the F15 will have a relatively short life, and will be replaced by a completely new model. The latest news is that this will happen late next year (2017), and will be designated model year 2018. As to when they'll be available in your part of the world (wherever that may be), I've no idea, but I think realistically you're looking at early 2018 onwards for most places. Incidentally, there will also be a completely new model, the X7, which will be the flagship of the BMW SUV range, on par with eg. the Mercedes GLS.