There are three main things I want from my iPad Pro (2nd gen 10.5").
1. Mouse/trackpad support. <--- This might be coming in iOS 13.
2. Full external storage support. <-- This likely will not be coming in iOS 13.

3. Default desktop version for websites. <--- This is likely coming in iOS 13.
Why?
1. For mouse/trackpad support there is some productivity software that would work much better for me on my iPad. Stuff like Excel/Numbers is really annoying with a touch interface. It's so much more efficient with a mouse. Also, my VPN software is basically non-functional with a touch interface. I can't get any work done with remote desktop type software with a touch interface. That means if I even have a small chance I might need to VPN somewhere, I need to carry my MacBook, not my iPad. Ironically, some of the VPN software options out there already have Bluetooth mouse support on iOS, but it's proprietary and only works in their software, and is very expensive.
2. It's pretty sad that I can't load in a spreadsheet or Word document via USB on my iPad at work and then do a minor edit and then put it back on that USB drive, even though I have a USB 3 dongle that can work with USB drives (for photos and video). At least with most of my spreadsheets and Word documents I can sometimes work around it with email and cloud storage, etc. but it's a PITA. OTOH, with large presentiations or video files, I can't do this easily. USB storage support would be so much simpler.
3. We can work around this already, but it seems bizarre that the default is still to get mobile websites on iPads. It's about time this is coming, since we've needed this since about 4 years ago.
Right now I am carrying my iPad Pro 85% of the time. Once these three things come, it will be 95% of the time.
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Note that even if Bluetooth is not supported, one workaround is wireless RF. On the 3rd gen iPad Pros, it would just mean a small USB-C RF dongle. On the Lightning iPads, it would mean a USB adapter, and then the RF dongle. But yeah, it would be annoying if it's USB-only, because Bluetooth support would mean no dongles necessary.
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BTW, once these three things come, and the iPad Pros go 6 GB across the board, I'll be inclined to upgrade from my 2nd gen iPad Pro. Otherwise I don't see much point in upgrading for my usage. YMMV.