We get this question almost 10 times a week. I wanted to clear things up and let you know that this change is only going to affect application development. Your Fan Pages will function just as they do now. The FBML will still work just as it does now as well...
Facebook made an announcement back in August that they would be moving away from the massively used FBML application, and moving toward iFrames which is true however it only affects canvas applications and Facebook page tabs...and that is from a development standpoint as well...
The way that you can create tabs now as an admin will continue to work the way they do now...and I always tell people who ask..."can you imagine if Facebook did away with FBML tabs, they would put almost every business fan page out of commission and lose so much revenue in ONE single day, that even if they DID do it, they would change it that same day because businesses are their only income".
So just keep on building your Fan Pages and creating new tabs...and if they do happen to change things down the line, well that seems to just be how Facebook rolls and when that happens you can come back to the blog and tell me that I don't know what I am talking about! LOL
Here is a quote from Namita Gupta from the Facebook Developer blog:
If you are interested in keeping track of the changes Facebook has planned for the future, you can do that from this link: http://developers.facebook.com/roadmap.
[UPDATE] Here is the latest from the Facebook development team regarding these future changes.
End of Year Deprecations, Page Tab Update
In August, we announced that we are deprecating some infrequently used APIs and FBML tags at the end of the year. We encourage developers to make the necessary code changes soon, because these may be breaking changes.
We will continue letting developers create new FBML Page tab applications until Q1 2011, because we are still working on the iFrame implementation. We are also postponing the deprecation of fb:board until we offer the ability to export data.
NEW UPDATE 12.05.2010: I asked the question on the Facebook development blog and Facebook actually answered me with this
Douglas Purdy of Facebook:
"I'll be very clear...
1. If you have an existing FBML page tab application, your tab is going to keep working.
2. I'll repeat, your tab is going to keep working now and after Q1 2011
3. That said, we want everyone to start using iFrames, so we are going to make all_new_page tabs and canvas apps using iFrames as soon as we can.
4. We had hoped that we would have iFrame for tabs ready this year, but we are not ready.
5. So we are delaying the roll-out until Q1 2011.
6. After we roll it out, we will have some period before we make it default for new apps.
Read more at blog.hubze.com
So that is DIRECTLY from a Facebook developer. Please pass this around to anyone you know who is wondering about this because there are so many mis-informed page admins that are freaking out! Hopefully this can put you at ease knowing that they are not even close to being ready...