The AAS reports that abortion opponents have an "ambitious wish list" for the upcoming session: 
. . . including a measure that would ban the procedure beginning in the 20th week of pregnancy.
That
 bill, which is still being written, would declare that a fetus can feel
 pain in the 20th week, an assertion many abortion rights supporters 
dispute. 
Other legislation — some filed, most still in the 
planning stages — would further regulate the use of abortion-inducing 
drugs, seek to cut off Planned Parenthood from any remaining Medicaid 
money and set up a system of stricter state inspections and audits of 
abortion clinics.
“We’re looking at a big pro-life majority in the
 House and in the Senate, so we ought to expect some big pro-life 
accomplishments,” said state Rep. Bryan Hughes, R-Mineola, a leading 
abortion opponent in the Legislature who is campaigning to replace 
Speaker Joe Straus, R-San Antonio, as leader of the House.
The Houston Chronicle reports on Governor Perry's news conference where he announced his support for legislation which would prohibit abortions after 20 weeks. A related bill has yet to be filed - no word on whether the governor will declare this emergency legislation. The governor implies that he is unwilling to take on Roe v Wade and claims that the decision allows for states to impose restrictions on abortion if there is a compelling state interest in doing so. Preventing pain is the compelling state interest: 
"Let me be clear, my goal - and the goal of many of those joining me 
here today - is to make abortion at any stage a thing of the past," 
Perry said. "But while Roe versus Wade prohibits us from taking that 
step, it does allow us, the states, to do some things to protect life if
 they can show there is a compelling state interest. I don't think 
there's any issue that better fits the definition of a compelling state 
interest than preventing the suffering of our state's unborn."
So the constitutionality of this legislation - should it be passed and challenged - hinges on whether a 20 week old fetus can feel pain. Here are a few sources that weigh in on this question: 
- Doctors on Fetal Pain.
- The Flawed Basis Behind Fetal-Pain Abortion Laws.
- Behind the Right's Fetal-Pain Push.
- ABA Journal.
- Do Fetuses Feel Pain?
- Abortion Rights Groups Absent on Fetal Pain Laws.