Are there other miners out there like me who are still turning a profit? When Bitcoins were $18 a piece I was making $300/month, now that the price is down I'm still making $90/month so I see no reason to quit. I initially bought more efficient hardware (80 Plus Gold PSUs and Radeon 5000 series cards) so my watt consumption is rather low. I am on the fence about building another rig at this time, I want to get another 5970 since the heat output will be negligible in the winter (just crack open the nearby door) but don't want to deal with that extra heat come next summer. The 7970s coming out have made me reconsider investing again so soon. My rigs are paid off at this point I'm just waiting to reinvest. I definitely will not be buying any more 6950s since their hash/watt ratio is nowhere near 5770s or 5970s so hopefully the 7000 series cards will be far more energy efficient.
I think in the medium term nothing can touch the 5970s and that includes the futue 7xxx series. The 7xxx series will likely close to double performance per watt and performance per $ however the prices will be back to full retail cutting into the value.
So while a 7990 will likely be in the ballpark of 2x the performance of a 5970 (or 6990) it will also be $750 to $800 making the hash per $$$ roughly the same or maybe a little worse. I bought some 5970s @ $400 and some used ones on ebay @ ~$350 simply because that is an amazing value even considering the potential for 7xxx series. After the 7990 hits I imagine many gamers will drop their 5970s on ebay so there should be a good market for me to cheaply expand hardware.
I am actually slowly getting rid of my 6950s and 6970s because the 5970s beats them in every category (density, price, efficiency). My goal is to consolidate my hardware (currently 8 rigs both open and closed cases with 3-6 cards of various types) into 6 standardized open frame rigs of 4x 5970s ea in the garage plus my watercooled workstation w/ 3x 5970 in the office. That should give me ~19 GH/s (maybe an even 20GH/s if I can tweak a little more out of em) at very low cost per MH and decent MH/kWh (~2MH/kWh).
Now on price per watt level the 7xxx series is going to rule however my electrical costs are relatively low (about $0.09 per kWh) thus my gamble is that lower capital cost is worth more than lower power costs (at least initially). At current difficulty a block costs me $90 in electrical costs. The price / difficult ratio would have to fall 64% from current levels (price falls or difficult rises) before I am below break even.