Remember PCs five years ago?
Exactly, not much changed except for multicore, and it's still underused. I'd not expect an average PC in five years to be anything unusual.
Mobile devices, on other hand, have a lot of way to grow. Maybe we'd see phones with HD screens and 1GB RAM in five years, and those would run whatever you'd wish.
A top PC from 2004 might look like: CPU: Intel Pentium 4 3.0 C @ 3.24 Ghz - Northwood Core 512MB PC3200 DDR SDRAM (400 Mhz) 160 GB Harddrive ATA-100 GeForce 6800 17" CRT Monitor
Now we would expect 8 times as much RAM and disk space. Far faster CPU's with for cores and a huge L2 cache. 4 - 8x as much RAM on a graphics card with 2700 GFLOPs vs 54 GFLOPs of processing power. And our monitors are both larger, lighter, and have a higher resolution. But, what's most interesting is we are far less CPU bound in 2009 than we where in 2004.
PS: A single i7 core would crush a Northwood Pentium 4 clock per clock even limiting it's self to the same instruction set. An 3.4GHz i7 has more floating point performance than a 2004 era graphics card (69 vs 54).
Note: I am ignoring the Prescott as it took a Prescott core overclocked to 5.2 GHz to soundly beat the performance of a 64-bit Athlon FX-55 that clocked at 2.6 GHz. http://en.wikipedia.org/wiki/Pentium_4
Most of the other advantages only come out when playing computer games or something like that.
And that is due to many of the 'moore's law' advances that have relatively little to do with javascript execution. (Small-screen quality, cpu/gpu/memory speed, improved communications chips and infrastructure, etc)
27-inch new iMac display (2560x1440) - 109 ppi
21.5-inch new iMac display (1920x1080) - 102 ppi
15-inch MacBook Pro (1440x900) - 113 ppi
30-inch Cinema Display (2560x1600) - 101 ppi
http://en.wikipedia.org/wiki/WUXGA
why we are going backwards: http://www.nytimes.com/2008/11/13/technology/13iht-13panel.1...
Moving up to 720p HD, 1Gb of memory and even quicker/more-cores chips doesn't seem more than a couple of years off. Whether they'll manage to make them any more usable is a different question :)
2. no iPhones
Sorry had to be said :)
Moore's Law still holds. Except we realized that doing what we classically did was not working out. Making CPUs faster causes heat problems and those are getting very problematic (remember when computers only needed a heat sink?) So instead of building a faster car, we just build more lanes on the road, so everyone can move quickly. Remember a 2nd core is almost double the capabilities, we just need software to catch up :P