Company willing to transfer H1b, but not sponsor GC

Thanks in advance:

I have the following question: I work for IT consulting company: my priority date is 03/2008. I-140 approved. waiting to file I-485.

I am looking for next project. One company is offering a job, but they only transfer H1b, not sponsor my Green card application. Should I take this job and bet the job market will improve in 2 years so the company will start to sponsor Green Card application again ? what is the risk ?

Thanks.