Personally, I doubt whether Apple will be overtaken by another company this decade, but anything can happen when a new entrepeneur excites backers with millions to invest. However, it is true that Samsung have overtaken Apple sales in one respect and Huawei became the second biggest phone seller in last quarter.
I think it is Apple's continued innovation that has brought its success and I have confidence that this hasn't wavered. Sales figures are only one measure of prominence. It is what is on the drawing board and in the planning department that will answer your question.
It is very highly doubtful that other mobile companies will have the ability to be able to take over Apple. Apple is one the most wealthiest companies in the world and the reason that is is because they are innovative and always stay relevant in their market. The recent woes of the iPhone X have started to bring on fears that Apple is losing a foothold in the mobile market but it certainly is not big enough to warrant other mobile companies from possibly taking over the company. Apple also has a very big research and development arm so you can best best that the next big innovation to come in the world of mobile technology or computer technology as a whole, Apple will have some kind of hand and say in it. The bottom line is that you can pretty much say that Apple will never be taken over by other mobile companies. They are no where near the size and scope of Apple regardless of what forecasters and projectionists are saying.