PC's will certainly continue to exist in the workplace. However desktop PC's are way too slow for serious engineering work. All of the real work I do is done on large clusters of servers that sit in a room on the other side of the world. I often keep 20+ expensive servers busy for hours on end... My laptop is simply used for typing, so anything that can connect to a keyboard would be good enough.
Word! In another thread, someone mentioned that this year's Black Friday computer specials involved costlier but higher performance machines. I feel that reflects how tablets and smartphones have been displacing low-end PC's, not mid-level and high performance (or business) PC's especially laptops.
This is even reflected at Apple, where the plastic-cased Macbook was ended when the Macbook Air came out, and they kept the Macbook Pro. (Disclaimer: I use a BYOD dual boot MBP with OS X and Windows 7, for personal and work respectively, and can travel for business with just one computer! And I run ESL SystemC simulations on Windows 7.)