Maybe Apple indeed think that Westmere is too small upgrade so they are waiting for SB to get early access and surprise us all (by that time Southern Islands from ATI should be out as well) with enormous update
This time around is like 2007, when they had an option for Quad core parts, creating the first run of Octad systems (all '06 DP systems were only Quads).
They only had to drop-in a new chip (didn't even need any changes in the firmware). They will have to update the firmware this time, but it's not that big a deal in terms of time or investments (unlike the Tick portion of the cycle, where the entire board changes due to the new architecture).
Due to that cost, Intel has created the Tick Tock cycle, as that huge chunk is amortized over 2 years (same boards = same chipset, socket,....).
By skipping the Gulftown parts, they're doing their MP segment a disservice, as some users (those that can in terms of finances, and may have been thinking about it for a little while on the whole, which more importantly IMO, includes software), switch over to a different OS and system vendor (i.e. Dell, HP,...).
In terms of raw processing power, it's about 50% faster

I know software is unfortunately lagging behind thus Sandy Bridge will be so significant (better clock fro clock, core for core performance).
Only under ideal conditions for Symetric Multiprocessing capable applications (can actually use
n cores, not limited to a fixed number, and not hampered by bottlenecks that may exist).
Real world performance won't be that much. More like what we saw between Harpertown and Nehalem's real world data (so 10% - 20% is more along what we'll see, and this is for SMP capable apps).
Single threaded applications would benefit, assuming the processors used are in fact what's expected/hoped for, as they've higher clocks for the same cost segments (P/N breakdown in terms of cost, and matching them with the initial cost for Nehalem parts). Same architecture @ a faster clock = better performance, single or multi-threaded applications. But single threaded could also gain a bit more due to Turbo Mode, assuming the other cores aren't loaded enough to prevent it from kicking in.
I don't know if HP and Dell still sell barebones kits, but there was a time that one could go to their sites, and get just the case, risers, boards; and pick up RAM, HDD, optical drives, GFX cards, etc. 3rd party.
I don't recall seeing that ability any longer, though it's worth a look.
I'm more accustomed to "bare bones" requiring a graphics card (assuming it's separate as it would be in a workstation) and HDD, though they're low cost enough most will upgrade them to what's needed, and keep them as spares (without any real complaint, though this may be to do with the fact it's usually funded by a corporate budget, not out of their own pocket

).
Has that been confirmed or is it just an educated guess made by PC Watch?
It's information that's out there, though the dates will change over time (usually getting later as time goes on). This type of information filtration is rather common, as Intel does release information to industry concentric sites.
I know there can be issues with Wiki, but generally speaking, it's gotten a lot better, and is a good source to find a good bit of information once it's available (articles get scrounged for info, and it's compiled/cobbled together at a single location).