They were forced to take half the payout in cash no matter what. It is likely that they will buy in the open market with that cash. It is very foolish to think they are walking away as some #$%$ bloggers suggest. They could have sold any time in the market before the deal was completed.
It's not really foolish to think that some will wait until the completion of distributions of cash and ETP before selling .... the cash portion received for SUN shares valued a share at $50. For the ETP portion they get 1.049 ETP for each SUN. So selling would have given a little less. Due to over-subscription for the all-cash option, nobody gets all cash. The cash/ETP mix will be some oddball number.
I don't know if people will tend to sell their ETP or buy more. Some will buy more ETP. SUN was a C corporation. Some former SUN holders will decide they don't want to deal with a K-1 and will exit. Others will be surprised when they receive a K-1 in March -- especially those who will have filed their income tax already. Ouch! 1040X time. A few of those may check here to see what that K-1 is all about.
I wonder if the SUN basis is going to be properly carried into the ETP capital accounts. Come to think of it, I don't even know what income tax implications of this are. In similar situations I think that a capital loss is suspended until all of the resulting interest is disposed of. Some study is needed I think.
Since Sunoco was a LP ??, it may be they have to pay tax on the difference between the total value received. I received stock for a LP years ago and the tax was basis on the difference between the value of the stock received and the cost basis after write downs in the LP. For some ETP owners, this could be the entire amount. So, it would be at least 15% plus any ATM and state tax. For some it would be close to 25% or $12.50. So they would have about 1/2 their cash left to buy ETP. However, I doubt that all these LP owners will go for ETP with other choices available. Also, you can not have zero basis which is what some might have in SUN.
Anyway, after the nice bounce today the big test is when the new units are distributed next Friday with cash. Only time will tell whether this is a dead cat bounce or a trend back up.