And if PS4's lead continues to grow, with XBone sales dropping off disproportionately after initial enthusiast/early adopter demand, PS4 will gain additional advantage and sales just from the "buy what your friends have/play" dynamic. MS was also able to extend their initial lead last-gen because their major advantage in install base meant they had the bigger game library and continued to attract more 3rd parties well into the gen, even after PS3 reached it's "turning point" it still had to make up lost ground.
But again, there is no reason to think this rumor is true. There has been a flurry of news about leaks from MS, and those leakers' identity being discovered by MS. Selectively providing false info to suspected leakers is the obvious way to prove they are the leaker. Dropping the BluRay drive would itself not save a signifigant amount of cost, certainly not $100. While it might prevent 2nd hand sales and thus boost long term profit, that would also destroy MS' retail partners' profits and create major problems in relations there... when MS is certainly relyin on retail partners right now to keep sales solid.
Both Sony and MS can be expected to drop prices in tune with reductions in production cost... Last I read, this gen should be able to do so quicker and more often than last gen, due to the basic hardware being very similar to standard PC hardware. CPU/GPU fab continues to progress, and they both should switch to a smaller process node sooner rather than later. That will help both of them sell more, just because more consumers are open to a reasonably priced console (and one with more games by that time). That aspect doesn't really affect the proportional share of each console though, and as long as MS retains Kinect that will be a disproportionate restraint on reductions in production cost. Incidentally, Sony just bought a memory producer so should soon be able to produce GDDR in-house, making any MS advantage in DDR vs. GDDR less relevant.
This is fairly significant although early adopters dictating what their friends buy over say the next year or so is far from given. One could arguably say that the year lead the XB360 had over the PS3 resulted in a more robust XBL userbase during the first year of the PS3, but one could just as easily explain this by pointing out that PSN simply wasn't on par with XBL at the time. The cost difference was a hard sell as well.
Dropping the optical drive on the other hand, would have little to do with shaving costs and everything to do with being the sole distribution outlet for both software and media. MS would pretty much have to sell specific game voucher cards in addition to XBL money cards to sell retailers on stocking the SKU, but I'd be curious to see the buying trends on these. From what I would gather, the primary consumers of money cards or game download cards would be those who don't have credit cards (not an insignificant number) and a smaller pool of consumers who use them as gifts.
As for other cost shaving measures; this was more what SCE had to rely upon simply to reduce losses. They had to shave $100 off a $600 console that was still costing them over $800 to produce in 2007. They saved some on manufacturing costs by cutting the PS2 Emotion Engine CPU, 2 USB ports and the media card readers and later dropped the PS2 GPU along with the CBE and RSX die shrinks, but they were still losing money off of every unit sold until 2010 if memory serves me correctly.
MS, on the other hand, not only hit profitability sooner per unit, but was also able to avoid a series of price cuts simply to spur sales. The original MSRP was $400 for the "Pro" and $300 for the non-HDD "Core." Technically, MS only dropped $100 off of both the price of their standard SKU (just console with HDD; currently the 250GB SKU) and $100 off their entry price SKU (currently the $200 4GB SKU). Granted, the same money bought better and better features (bigger HDD, HDMI port, NAND memory, standard wireless constroller), but it doesn't change the fact that MS essentially only dropped $100 off the original 2005 prices, which is pretty incredible over 7 years.
By contrast, the PS3 went from $600 and $500 SKUs all the way down to the current $250 and $200 SKUs. They had to cut MSRPs before redesigns and streamlined manufacturing processes could bring them into profitability as a result.
We'll see how quickly both manufacturers are able to cut costs with new designs and streamlined manufacturing, but they're already starting from lower points from a parts/manufacturing cost standpoint. I've seen discrepancies on the BoM estimates, but I estimated the PS4 was closer to $300 before teardowns were even available based upon the reported builds, but I've seen estimates that have it pegged closer to the $400 MSRP. MS is always going to have the handicap of the Kinect 2.0 as an added cost until they offer a console only SKU.