It appears that previous rumors of Apple exclusively moving to use Intel for 2018 iPhones has gained traction. Latest research note from well-respected analyst Ming-Chi Kuo of KGI, obtained and reported by 9to5Mac, shows that Apple would like to completely eliminate its reliance on Qualcomm modems for its iPhone, and instead partner with Intel to start providing the modems it needs.
One of the main reasons why Apple and Qualcomm are budding heads is due to ongoing legal disputes. One of the lawsuits between the two companies, launched by Qualcomm, alleges that Apple improperly shared its proprietary code with Intel. Due to this, Kuo's indication of Apple working closely with Intel also makes sense and holds weight.
Intel may enjoy exclusive orders from Apple, but only for a short period of time. Apple may still approach Qualcomm for some orders as it negotiates concession in trying to lay legal disputes to rest.
Apple is famous for not trying to rely too much on individual suppliers as it gives too much leverage, and the company constantly tries to push for a more diversified supply chain, where it can. Apple has also preferred to build and design its own parts, much like how it recently switched to making its own GPU.