We like it when people play fair. In this scene, we discover the witches haven't dealt fairly with Macbeth. He has been duped, as we all have at some point, and we have a moment of strange compassion for that aspect of this story and this protagonist. It doesn't last very long, of course, because it can't. We like it when people play fair, remember, and Macbeth has not played fair from the very beginning. But for that moment--and for me, again in the castle when he practically begs Young Siward not to provoke a fight with him as he's already a soul condemned to hell and doesn't need even one more iota of guilt and sin on his conscience--we do feel some sympathy for Macbeth.
You have asked a really interesting question, because one of the reasons why this play is so compelling is the dignity that Macbeth dies with and the way that we as an audience do sympathise with the fall of this tragic hero. However, it must be said, in this scene, Macbeth gives little ammunition for the audience to sympathise with. Instead, he seems to get exactly what he asks for, and then goes on to commit a heinous crime in response to the apparitions that the witches conjure up for him. Consider how he addresses the witches:
I conjure you, by that which you profess,
Howe'er you come to know it, answer me:
He goes on to say that even if Nature destroys itself in consequence, he still urges the witches to obey him. The apparitions that appear give Macbeth the half-truths he feels he is looking for, but it is when he has asked his questions yet insists on finding out if Banquo's heirs will have the crown that we might be lead to feel some sympathy for him. Note how the witches say to Macbeth before the vision of eight kings with Banquo following, "Show his eyes, and grieve his heart". Macbeth is definitely grieved by what he sees:
Horrible sight! - Now, i see, 'tis true;
For the blood-bolter'd Banquo smiles upon me,
And points at them for his. What! - is this so?
Perhaps the sight of Macbeth, realising that in spite of all his efforts he will lose the crown and not pass it on, and that Banquo's descendants will gain it, is pitiful, but it is doubtful whether we feel sympathy at this stage. Certainly his resolution upon hearing the news from Lenox that Macduff has fled to join Malcolm in England to slaughter his family puts him beyond the realm of sympathy until the last Act:
The castle of Macduff I will surprise;
Seize upon Fife; give to the'edge o'th'sword
His wife, his babes, and all unfortuante souls
That trace him in his line.
Note too how this represents a further escalation of his crimes - this is no longer a subtle stealthy kill, as was employed to dispose of Duncan and Banquo - this is an open and outright act of cold-blooded and pre-meditated murder.
The question is all the more interesting because the issue of audience-sympathy has been raised in a scene where Macbeth, of his own accord, goes and approaches the witches in their cavern. He is totally under the spell of his vaulting ambition and wants to know more in order to achieve more after realizing his intial ambition of becoming the king of Scotland.
This is also the point after which the actions of Macbeth are going to become their cruellest self. His violence would become more and more pointless e.g. the order to kill Macduff's wife and children.
But, despite all this, I would say, the audience may still feel sympathy for him in act 4, scene 1 since they see a man who is not his senses here. He is completely trapped by the temptations of evil both outside and inside him. The very spectacle of Macbeth being equivocated arouses fear in the mind of the audience and in this fear there is a tacit identification, implicit somewhere in all this. The spectacle of Macbeth, being duped by the witches does make us feel for him a little bit, at least.