The trend is starting to go away from the aftermarket altogether, and will continue in the near future. Many people are coming to the realization that the aftermarket is a waste of money. Most slip-ons, and even full systems produce a HP drop (bottom end and top end), until the bike is tuned to that specific exhaust. And even with a proper dyno tune, the small HP gain up top will not be felt 'till quadruple any road speed limits. The small gains will only be felt on a track. You'll have all the HP, Torque loss in the bottom end where you can use it on the street gone due to loss of back-pressure and staggering.
The bikes of the past, the manufacturers (whether deliberate or not), always left room for improvement to leave some meat on the bone for the aftermarket to improve on their bikes. Thus leading to sponsors, thus leading to getting their bikes seen on race tracks around the world on TV, thus leading to sales. Same pieces, (exhaust, air filters, plugs, chains, brake levers, etc). But now, with manufacturers like BMW, Ducati and Aprilia, upping the barr, the big four have had to, and will continue to step up their game to build the ultimate superbike, squeezing out the aftermarket. It was done with cars (goodbye local Perrformance Improvements), it's now happening to bikes. Out-of-the-box, they are just too good to mess with.
Here's a 2010 Suzuki GSXR L0 being dyno'd with the typical upgrades. The mechanic is a good mechanic and is somewhat embarrassed (no fault of his own) by his own video. All that money $2000 + for 6HP:
http://www.youtube.com/watch?v=VWdRd-VeVyI
I have talked to this mechanic. He no longer uses Power Commanders or Bazazz.
For my own bike, I noticed an engineering defect with Suzuki with their massive cans. Besides the esthetics (looking hideous), there is a safety flaw. At high speeds, the air being deflected off of the cans in a straight line would be grabbed by cross-winds, and (scarily) cause the back end to step out. The M4 fixed that problem, and looks and sounds great. Suzuki clearly has to re-think it's exhaust systems.
Don't waste your money on Power Commanders, or bazazz units. If you go aftermarket exhaust, take your bike to Riders Choice and have them flash the ECU with their Yosh box and you will get a better result for half the cost.