Upgrade from 10-speed to 11-speed rear cassette?

Shimano road 11-speed until recently required a wider freehub - Shimano MTB 11-speed cassettes have always fitted as far as I remember. The exception now are the HG-700 and HG-800  11-34 11-speed cassettes which will fit on a standard 10-speed Shimano compatible freehub (the larger bottom cogs and spider dish will allow everything to clear the spokes).

Quite possibly more trouble than it is worth, unless you enjoy spannering, in which case have at it.

Any use ?
https://www.bikeradar.com/forums/viewtopic.php?f=40091&t=13093638

As per the comments above , with the wheels you could remove one of the cassette cogs and spacer, put the spacer are the back of the cassette and install....works fine but your left with a larger gap . Chainring wise they're be fine .

There are several issues here. Firstly your shifters won't work, as they have ten increments inside (the rh ones does anyway) and the lh one may have a different pull ratio anyway. You may also find that the rear mech you have wont work on an 11speed cassette anyway, and also your freehub may not support 11 speeds. You will also need a new chain. Overall its unlikely to be a cost effective way of doing things.

Along with the shifters you will also encounter issues with the rear derailluer. The derailleur’s shift-activation ratio is different for Shimano 11-speed rear derailleurs than it is for Shimano 10-speed rear derailleurs. ie; the lateral movement is a function of the design of the derailleur and the shifter.

Shifters will need a change AFAIK - you could avoid a wheelset change if something like the HG-7/800 11-34 cassettes would suit your riding (they fit on a 10-speed freehub like the other 11-speed Shimano MTB cassettes) but there's obviously slightly more gaps than an 11-28.

New wheels needed and possibly new shifters. R500 are ten-speed only. If you want to swap back to a compact it's easy enough, you may need to shorten your chain (you'll need a new chain to swap to a non-compact chainset)