Umm, yes. It will go down. Royalty trusts are unhedged and thus directly exposed to commodity prices.
However there may be mitigating factors:
-SBR is about 50:50 oil/gas in terms of current revenues (based on last distribution announcement)
-Producers with a higher liquids content get more than the quoted NG prices for their gas (because the NGLs are much more valuable), According to SBR's last distribution announcement which reflects gas production for September 2011, they received about $4/Mcf for their gas. That is probably not far from the Nymex price for NG in that month, so I would conclude that their gas is pretty dry and so they are exposed to falling prices on the gas part of their output.
-gas is priced differently at different geographic hubs, so the price received depends where their production is (at which hub their gas is sold). This was more of a factor in previous years however with new pipelines much of the geographic variation has been levelled out, so I wouldn't bother to consider this any more.
In conclusion: SBR's gas is probably mostly dry (based on the price they receive) so they are exposed to falling NG prices on the gas part of their sales. But they have significant oil production too and oil prices are still strong.
Do a back of the envelope calculation based on the last distribution announcement: oil: 35,154 barrels oil price per barrel: $91.37 NG: 754,371 Mcf NG price per Mcf: $4.07 This resulted in a distribution of ~36 cents
Now assume the volumes and the oil price stay the same but the NG price is $2.50. If my calculations are right, trust income would go from $6.3m to $5.1m for the month. That implies the 36cent distribution would be reduced by about 20% to 29cents by May (distributions lag by about 3-4 months).
Of course the volumes will vary from one month to the next, but I conclude that in a few months, SBR distributions may fall by about 20% which is not the end of the world. If gas prices fall further then so will the distribution.
See how much you can conclude from a simple reading of the distribution announcement?
Natural Gas (NG) is sold dry, always dry. Coming out of the well the NG goes through slug catchers that separate the liquid from the gas. More the NG pressure goes down more the liquid separate. The liquid is very valuable and is used in jet fuel for example, but is sold separately. The price vary with the retail usage. In the US there are few urban area that have a NG installed distribution network. The north east, SFO area, LA area etc. The farm land of the middle west use butane or propane gas. There are not enough pipelines to move the NG from the gulf coast to the north east. This is changing with the shale gas found the north east. This is why LNG trains are planned , to export LNG. The Jones law limits the transport of any goods from a US port to another US port. The vessel must be US flag.