This is NOT a question of which party wins the 2028 election. This about whether real control of the White House switches parties.

Ex: If Trump is inaugurated in 2025 and refuses to leave the White House in 2029, and the Dems are unable to force him out, market will resolve NO.

"The White House" is being used figuratively to include the general trappings of the executive branch, things like being the person who meets with foreign leaders, controlling the nuclear football, being able to veto bills. If Trump holes himself in the physical White House while losing control of the executive branch, this would not constitute "control of the White House."

If the United States government enters a post-constitutional phase, I will use vibes to decide which party "controls the White House". For example, if Antifa overthrows the government, that will constitute a change in control of the White House.
If parties cease being relevant, I'll use a general-ally vibe test. For example, if Trump hands control of the White House to his unaffiliated son, that would not constitute a change in party control of the White House.