Does the ability on the 7 (Treasure) provide an ongoing effect that affects future tricks?
No. The text on all the cards describe universal rules that are only relevant to the trick in which the card is played. Everyone always scores exactly 1 point for winning a 7 (Treasure). Since there are three 7s in the deck, there are only 3 points available each round from winning 7s.
From The Rulebook
When do the abilities on the 3 (Fox) and 5 (Woodcutter) occur?
Each of these two abilities takes place immediately when the card is played, before another card is played or the winner of the trick is determined. (Note: If the person playing a 3 changes the decree card, the trump suit may also change. The new trump suit is used to determine the winner of the current trick.)
If my opponent leads a 9 (Witch), do I have to follow the 9’s suit or the trump suit?
You must follow the 9’s suit if you can. A non-trump 9 is not treated as if it were in the trump suit until after both cards in the trick have been played following the normal rules.
If my opponent leads a trump card and I have a trump card, can I play a non-trump 9 (Witch)?
No. A non-trump 9 is not treated as if it were in the trump suit until after both cards in the trick have been played following the normal rules. If you can follow suit with a trump card, you cannot play a non-trump 9.
Who wins a trick with two 9 (Witch) cards in it?
The special ability on the 9 (Witch) only applies when the trick contains one 9 (Witch). (The witch’s magic lets her transform into the trump suit at the end of the trick, but with two witches in the trick, they neutralize each other’s magic.) If the 9 of the trump suit was played, it would win; otherwise, the 9 of the lead suit would win.
Who leads the next trick after a trick with two 1 (Swan) cards in it?
If both players play a 1 (Swan), the player who loses the trick would lead the next trick.