I will continue using WP for its ability to allow my X3 phone to be a mobile extension of my PC which is much simpler in the Microsoft ecosystem than from other mobile operating systems. I've been on windows phone since the Samsung i-730 (running windows mobile 2003) that's a span of over 15 years. I bought that phone for the simple reason that it was one of the first smartphones having a version of office which could also sync and edit files from my PC. The Excel version ran most of my formulas except some database and nested lookup functions. There were no apps then, you simply went to the website for your URL connections. When Verizon discontinued carrying windows phones, I kept using mine until phone technology advanced and calls started dropping on my commute. By that time the Lumia 822 was being carried and I upgraded. The office version on that phone was terrible being nothing more than a glorified file viewer with minimal editing capabilities. For Microsoft who won the office wars to put out a product like that was shameful. I used that until the screen broke in a fall and Verizon replaced it with HTC OneM8. When the M8 was not upgraded to Windows Mobile v10 (another shameful performance from Microsoft as is dropping Window Mobile) I kept using it waiting for Verizon to offer an upgrade.
That was supplanted by the unlocked X3 about a year ago when it was on sale dumping Verizon (no windows option again) in the process. The X3 is a great phone, it syncs with my PC, I can attach my Plugable docking station to the HP doc giving me a mobile PC when also attached to my monitor. The Excel and Word versions on it are the best since my Samsung phone now allowing copying and editing of complex formulas. As far as apps go, if not available in the store, I simply connect via the web just like I originally did. Phone functions work well and the mobile OS is very stable and receiving patches through 2019. An SD card holds all my photos files, and music. The AkrutoSync program on my PC allows seamless synching over home wireless network of outlook calendar and contacts between PC, phone, tablet without using the cloud. At this point, I see no reason to upgrade off of Windows mobile. Not impressed with the I-Phone from work and want nothing to do with Google ecosystem. By 2019, Microsoft will have to have something available in the mobile space as they can not ignore it. I’ll see what I want to do then. Finally, if your current tech hardware does what you need it to do, there is no real reason to upgrade.