Thanks for your answer. But I have several questions now, coming from your answer:
What is the alternative proposed by Adobe, with similar features?
Will the CS6 version, to which I intend to upgrade, include Catalyst CS 5.5?
How can I import the file in stages and import it in Catalyst CS 5 version? I don’t see any Merge option in the Menu.
If you can help me with these questions I will be very grateful to you.
Flash Catalyst will be in any future version of the Creative Suite.
In terms of replacement... For Flex development there really is no replacement. The best you can do it use the current version and import it into Flash Builder. Round trip editting was broken with the 4.6 release of Flash Builder. For prototyping, you can review a whole host of alternatives. Some are better than others, but a lot depends on what you are prototyping.
As to your import issue, there is no merge. Import each cluster into Flash Catalyst, then you can select all the elements and create a Custom Component. This will help in managing it as to work with it.
Realize, if your illustration is that complex, you may have rendering and performance issues.
Thank you for answering, there's one thing I still don't understand.
I have creative cloud now, and I work on illustrator to design UI and pass it to the developer who creates the interactivity. Is this method of work no longer possible with any Adobe product? e.g. draw the whole page with buttons and scroll bar, then program the buttons and the scroll bar to do what they should do.
The question is in what development language is the developer working in? If it is Flex, then you can keep on using Flash Catalyst. It just won't be updated. If you are migrating to the web stack (ie: HTML/CSS/JS), then your options are limited. Fireworks does support some CSS3 attribute extraction, but there is nothing as integrated as the FC-FB tool chain.
Web development is going to require more work for both the designer and the developer.