Not that I want to be pessimistic, but I very much doubt that MI5 will be made in the near future, if ever. I would love for it to be made, I just doubt it will be.
Sadly, I have to agree with you.
As a matter of fact, I don't know if LucasArts will ever resurrect the Adventure genre in his games; by today's standards, those game are not exactly "long-lasting". You buy it, you finish the story-line, and that's it. If you ever get to replay it, it will be many months later (or maybe years). That's why multiplayer games (such as Warcraft III, Unreal Tournament, etc.) are quite successful; you can finish the main story-line, but that's just the beginning: Endless hours of online play await.
I would REALLY love to hear the official announcement of MI5, but we'll just have to wait and see...