Attorney Vaisman is absolutely correct. With the pending I-130, it is unlikely a B1/B2 will be issued. If they already have a B1/B2 in hand or the consulate issues a new one, CBP can deny them entry when they present at the border/airport and be returned to their home country. It is better for you to visit them.
It would be a waste of air fare. CBP (Customs & Border Protection) will not admit them if consulate processing of an I-130 is pending. Admission on a B-2 visa by CBP is contingent upon the foreign national proving that he does NOT intend to immigrate to (and remain in) the United States. Under U.S. immigration law, CBP cannot admit a foreign national if there is immigrant intent. If you parents attempt to visit you, it will not be a pleasant experience for them.
If you have additional questions, you can always contact an immigration lawyer, whether myself or one of my colleagues. If you appreciate the time spent preparing this answer, kindly consider marking it BEST ANSWER or HELPFUL. Good luck to you.
Dean P. Murray
The Murray Law Firm
560 Sylvan Avenue
Englewood Cliffs, NJ 07632
Mr. Murray's response is NOT legal advice and does NOT create an attorney-client relationship. You should NOT rely on this response. Mr. Murray's response was generated without conducting a full inquiry as would occur during a face to face attorney-client consultation. It is likely that the response above may be made less accurate, or become entirely inaccurate, as you, i.e. the questioner, disclose additional facts that should only be discussed during a private consultation with an attorney. I strongly recommend that you consult an attorney who is licensed to practice law in your state (or, in the case of immigration law, and attorney in ANY state), whereupon all relevant facts will be discussed. All responses posted by Mr. Murray on Avvo.com are intended as general information for the education of the public, and not for any specific individual.