Please not this again. People say this every patch and it never happens. When a stable version of Forge is released, that's when most mod makers will abandon 1.6. 1.7 had massive code changes, much more than any other patch, and it's my understanding a stable version of forge will likely take a couple months at the minimum based on what he was tweeting. There is no way they will skip 1.6 and go straight to 1.7. We are talking at least half a year for most mods to be ready, and stable modpacks much longer than that. With the increased size of the Minecraft team, and more work going towards the official API, you can bet that 1.8 or maybe even 1.9 will be released before many mods are ready for 1.7. Also, expect internal changes for 1.8 and beyond to be very large too, completely breaking each and every mod every few months.
I'd actually wager the opposite. 1.6.4 will likely be the golden version for minecraft modding until the official API releases sometime in 2014, that is, if you like playing with lots of mods in a stable pack. If I was making mods, I definitely would not rewriting my code every 3-4 months as progress towards the official API is made... then have to rewrite completely for the official API. I would just wait for the official API, and focus on 1 version of minecraft while the major changes are happening.
Just imagine how much further the modding community could get if we focused on 1 version and waited for the official API to move on. All that time rewriting mods over and over could of been used for balancing and making new content. It's no surprise many modders burn out and pass their mods to another team.