All microprocessors can only do one thing at a time, but they can do it very fast.
I made a setup wit 16 (slide) pots read by two 4051 multiplexor IC's
I was able to read all 16 pots and format the read values and send them over serial to a PC program in 10 ms. That translates to reading 16 pots 100 times a second. Enough ? 
Here's a link to a zipfile on my website with schematics, PCB layout and Arduino code.