Should I buy Anno 1404?

Hi,

I've never bought a game without a sale so far. Also I've never paid a price beyong 4,99 €.
Now I've seen, Anno 1404 has come back to steam. I used to play Anno 1602 and Anno 1701 a long time ago and I loved it! Now I'm thinkig about buying Anno 1404.

It's 10 € for the basic game and 15 € for the gold edition, including the Anno Venice Addon.

Should I buy now? Will it be on sale? Will there be a autumn sale on steam?
Furthermore, is the addon worth it?

greets from germany