I've become such a Zeiss Batis fanboy, that I couldn't help myself: just bought a Batis 135mm.
I bought it because:
1. The Batis 85mm has become my favorite lens and I'm often wanting just a bit more reach.
2. Reviews, like Dustin Abott's, have been absolutely stellar.
3. Shares the same the filter thread as the Batis 25, 85, and Sigma 35mm...this has become a really important thing for me.
4. Love the lightweightness...it will be a perfect fit for my Think Tank Photo Urban Approach bags. A 100-400mm GM would be super cool, but I know myself: whenever I own a telephoto zoom, like 70-200 or 100-400L, they mostly sit in the bag. They're just a hassle. The Batis 135mm is light/small enough that I can walk around with it plus 2-3 other lenses.
5. The worst thing about the 135mm is the ridiculous price, so finding a used one really helps. I still paid more than I'd prefer, but saved a few hundred $$$.
To offset the costs, I'll be putting my Laowa 12 and Sony 55 for sale. The 55mm has been trouble for me on the filter issue. I don't yet own a 49mm filter, and thinking about adding one (or even a step-up ring) makes me cringe...just don't want to go there. It's a pretty awesome lens though.
If my calendar image sales go well this year, I hope to add the 12-24mm (another reason I need to sell the Laowa).