UFC announced it via Twitter 18 minutes ago:

UFC Houston Alexander's replacement against Andre Gusmao will be TUF Finalist Krzysztof Soszynski. http://98.ufc.com18 minutes ago from web

The UFC 98 site has also been updated:   Krzysztof Soszynski Vs. Andre Gusmao
	Name: Krzysztof Soszynski Height: 6' 1" (185 cm) Weight: 205 (93 kg) Record: 18-9-1	"The Polish Experiment"		Name: Andre Gusmao Height: 6' 2" (188 cm) Weight: 205 (93 kg) Record: 5-1-0
May not be broadcast. Click for details.

This is a quick turnaround fight for the Polish Experiment--he just finished beating  Brian Stann via Kimura at 3:53 in the 1st. He didn't take much damage or fight a long fight against Stann, so maybe he figures he'll just roll last training camp into this one. Very different opponent though who presents a whole different set of challenges.