This morning I had the same issue and tried the following - it worked!
- Right click wifi icon
- Open Networking and Sharing Centre
- Change adapter settings
- Right click Wi-Fi->Properties
- Configure button
- Advanced tab
- Wake on Magic Packet - change to DISABLED
After I applied this - it reconnected without having to reboot.
I forced a sleep on my laptop, brought it back up, and it was still connected quickly.
Too soon to say if this workaround will always work but it saved me a reboot today which is worth posing!
Cheers.
UPDATE:
The magic packet has nothing to do with the solution. It seems that simply changing an adapter property and applying it recycles the WiFi adapter and gets it connecting again.