Do you plan on acquiring 2-vechiles once the lease is up?
If not, a $10,000 purchase (financed) should not affect your DTI for a home purchase; assuming the "new" payments are less than the lease payments.
If you plan on financing/leasing 2-vehicles in Dec, then your DTI will decrease and may reduce your mortgage loan amount, and may also affect your interest rate due to the credit inquiries. However, you can offset the morgage loan decrease with down downpayment.
If the lease expires after your settlement date, you won't have anything to worry about.
But it sounds like you already have a plan in place if the lease expires before the settlement date.