Cuban said there are three major stakeholders in the ACA that could take a hit from a repeal: insurers, health-care providers, and consumers.
"Who is going to take less?" Cuban asked.
"Are the health insurers going to say, 'You know what, we'll take fewer profits? No. Are the health care providers going to say, 'You can pay us less?' Well, they've already been crushed in that manner."
As a result, Cuban argued, the burden will shift to consumers.
"There's not a whole lot left to pull out of there, so it's going to fall on the consumers to get less coverage in some matter or another," Cuban said.
Republican lawmakers have proposed rolling out what they have called a "patient-centered" program to replace Obamacare, one that they say will come at a lower cost to the federal government.
Obamacare has expanded health coverage to about 20 million people by, among other things, allowing people under age 26 to stay on their parents' health plans, and by issuing federal tax credits to lower the costs of premiums charged to most customers of government-run insurance plan marketplaces.
The ACA also has given federal dollars to states that have agreed to expand their Medicaid programs to cover nearly all poor adults.
Republican talk of a replacement for Obamacare has raised fears that Medicaid expansion in 31 states would be rolled back, or that states would be given less money than they have received to fund that program.
Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank," which features Mark Cuban as a judge.