If I remember right, the G20 summit is on monday. I think we could have important information on the future of bitcoin regulation announced on tuesday the 20th of march, 2018. Altcoins could have a positive effect on bitcoin's price. They provide additional network transaction bandwidth and a medium for transmitting crypto quickly with low fees.
The media could be attacking bitcoin. There was the "tether(USDT) conspiracy" where the media claimed $80 billion in tether was being used to buy bitcoin in an effort to artificially inflate its price(it helps if you know tethers market cap is only around $2 billion). Now the media may be pushing something they're labeling the "bitcoin death cross" you can read about it here:
Image link: https://assets.bwbx.io/images/users/iqjWHBFdfxIU/iCW5G0POCvEI/v2/800x-1.png
https://www.bloomberg.com/news/articles/2018-03-16/bitcoin-s-death-cross-looms-as-strategist-eyes-2-800-level
Anyways there a lot to be said about this. A lot of different potential angles.
About tether - Rumors are that exchanges are going to delist tether and bring in proper USD. Some say another crypto, alternative to usdt might also be a possible option.
About the price downfall - One reason is that the whole Mt. GOX trustee issue, Mr. Kobayashi and his shit that he is dealing with. Another is the obvious one that almost everyone stated, panic selling. Eh fuck people.