The post is a bit confusing, though, because well before you get to the line that you quoted, the article states:
"And we’re upgrading all Linodes to 8 cores! Right now. As in all you need to do is reboot to double the computing power of your Linode. By the time the host refresh is completed the average Linode will be running on hardware that is less than 1 year old."
I, for one, thought that it was ready now after reading that. In fact, from the comments, it's clear that for some customers, this is in fact ready:
"BizzarTech: Rebooted my 1024 and moar cores!!! Thank you!!"
No, the move to new hardware and increase in the number of available cores is separate. If you reboot right now you'll get access to more of the 'cores' on the host system (though I suspect they're really just "threads" in Intel terminology). But you're still running on the older L5520 hardware.
processor : 7 vendor_id : GenuineIntel cpu family : 6 model : 26 model name : Intel(R) Xeon(R) CPU L5520 @ 2.27GHz stepping : 5 microcode : 0x11 cpu MHz : 2266.746 cache size : 8192 KB physical id : 0 siblings : 8 core id : 0 cpu cores : 1 apicid : 0 initial apicid : 1 fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 11 wp : yes flags : fpu de tsc msr pae cx8 cmov pat clflush mmx fxsr sse sse2 ss ht nx constant_tsc nonstop_tsc pni ssse3 sse4_1 sse4_2 popcnt hypervisor bogomips : 4533.49 clflush size : 64 cache_alignment : 64 address sizes : 40 bits physical, 48 bits virtual power management: