Upkeep Triggers

[ISBPathfinder]

So, I am looking at Phyrexian Soulgorger and Drifter il-Dal from a donated standpoint with Jon Irenicus, Shattered One. It looks like the sacrificing them option is out the window due to Jon's effect but can opponents choose to do nothing with those cards and just blank the upkeep triggers as a whole choosing the sac option but failing to do so or how does this work?

Sorry I keep asking questions on this commander, I keep failing to get my head around all the angles.

[WizardMN]

They are not forced to pay either cost. If they choose not to, they will be instructed to sac the creatures which they cannot do. Ultimately, they will choose not to sac anything and will get to keep the creatures. So they are not the best things to be donating.

The rule in question for the Il-Dal situation anyway:

118.12a. Some spells, activated abilities, and triggered abilities read, "[Do something] unless [a player does something else]." This means the same thing as "[A player may do something else]. If [that player doesn't], [do something]."

[void_nothing]

If a Phyrexian Soulgorger, for example, is under Jon's effect, then its controller can freely not pay the cumulative upkeep cost. Nothing will happen as the CU triggered ability resolves, because it's not a choice of whether or not to sacrifice the permanent, it's a choice of whether or not to pay the cost - sacrificing is simply an effect and is being prevented by the Irenicus-granted static ability and, ultimately, by CR 101.2.