Can an employer extend date of severance package pay out after contract is signed

I was laid off by my company, per my severance off I was to be given my regular salary from 10/15 to 12/15 with full benefits, on 12/15 I was to be paid out for 2 months of salary, repaid for school tuition as my severance. I was contacted by HR informing me due to a change of business I would get my regular pay check on 12/15, another one on 12/31 and they were extending my payout of severance to 12/31 due to a change in business. I have not worked for this company since mid September. Per my severance package I would remain on payroll for 2 months 10/15 to 12/15 and then would get my 4 weeks of pay from years of service and 4 more weeks of vacation pay as my payout. I am concerned about a change since the contract was signed, is the company extending the contract to avoid paying me out due to filing bankruptcy, are they calling people back, or unable to pay offers? I was a full time employee not a contact position.