Of course that's true. If you are serious enough, you can develop for any device. The question is, does it make sense from any perspective?
Realistically speaking, it's going to cost me a $1,000-$10,000 more to develop for 5.1 rather than develop just for 7 (extra device, extra design, extra testing time, potentially extra development time). If you didn't originally develop for 5.1 and it doesn't cost you as much, you are not serious (or severely underestimate your costs).
I'm not developing apps for iOS, but I'm not sure if I started tomorrow, and released (say) in two months, that it would be financially justified to target 5.1
Realistically speaking, it's going to cost me a $1,000-$10,000 more to develop for 5.1 rather than develop just for 7 (extra device, extra design, extra testing time, potentially extra development time). If you didn't originally develop for 5.1 and it doesn't cost you as much, you are not serious (or severely underestimate your costs).
I'm not developing apps for iOS, but I'm not sure if I started tomorrow, and released (say) in two months, that it would be financially justified to target 5.1