Tesla is the first manufacturer that is gradually losing the federal tax credit, because it was the first to cross the target of 200,000 plug-in car sales (in early Q3 2018). The second manufacturer is GM, which is one quarter behind Tesla.
The new amount (25% of the full $7,500) will stay available through the end of this year.
At this point, it's not clear how Tesla will deal with effectively a $1,875 higher cost for consumers. Previously, Tesla decreased prices when the credit moved from $7,500 to $3,500.
A lot will depend on the demand in Q3 after surging in late Q2.