Does anyone on here actually MAKE prints? I'm serious: people talk about resolution, ppi, etc. but the proof is in the print.
I was a full time professional photographer for 35 years, the last 9 of which were digital. I sent a .TIF file from my Fuji S2 to my printer at the time (now out of business, sadly) of a family. I requested a 30x40 print. The owner of the lab called and asked, "Was that a negative that you had scanned into a digital file, or was it an actual digital image?"
I told him, "You have the file...can't you tell?" His reply: NO! The print is sharp and gorgeous. Could I display this print for two weeks in the entry to the lab?" I said, sure, no problem. He set up a ballot box with a sign that said, "Please vote: is this FILM or DIGITAL?" 68% of his clientele, consisting of professional and advanced non-pros, voted FILM. Keep in mind the Fuji S2 was a 6.2 Mp camera...
Some months later, I ordered a 40x60 print from a Canon 20D camera. Same thing: can I display this? Yes, I told him. Same voting. Different results: 72% thought it was film. And as far as the billboard comment goes, I hate to burst anyone's bubble, but I had a full length bridal image that filled one third of a billboard...and it was made from the Canon 20D.
What people are missing is the fact that the software of the printing equipment does a very admirable job in up-sizing these images. Canon has announced a 50 Mp camera...but I won't be a buyer. Remember the largest print in the world at that time was displayed in the Photography Hall of Fame and Museum in Duratrans media. It was made from a 6x9cm film negative (probably equivalent to a 40 Mp file).
I don't know about all of you, but I have yet to have the need to make a print 12 feet tall and 40 feet long (or whatever the size of the thing). However, camera makers have done an excellent job in pushing the "More MP = More Quality!" mindset.
The moral of the story: stop chasing the Megapixel Monkey! Unless you are making fine art seps, that 18.2 MP Canon Rebel T4i (or whatever camera--just an example Nikon/Sony/Panasonic/Pentax fans!) is going to be more than enough for you. You will see very little...if any...appreciable difference from an 8x10 to a 24x30 at the equal appropriate viewing distances.