The Namibian full-backs have been on the fringes of the Premiership side's squad this season, making only two appearances between them.
Botha, 27, has had his time in Devon disrupted by a broken leg and dislocated ankle in November 2014.
McGuigan, 26, was signed as a result of Botha's injury and has scored four tries for the club.

Jake Vallely, 24 - who had described himself as "the hardest man in Brecon" - beat 20-year-old Private Matthew Boyd to death in May.
Pte Boyd's mother Michelle Rogers said her son's death had caused "unbearable pain".
At Cardiff Crown Court on Thursday, Mr Justice Lewis said the killing was a "savage and senseless attack".
Vallely was found guilty of murder on 1 December following a two-week trial.
After a night of drinking, the former boxer had pursued Pte Boyd through the Powys town before carrying out what Mr Justice Lewis described as a "sustained attack on a young man lying defenceless in the road".
Pte Boyd, who is originally from Carrickfergus, County Antrim, had been in the town for training exercises at the infantry battle school.
Sentencing Vallely, Mr Justice Lewis told him Pte Boyd was "entirely innocent and did not provoke you in any way. You chased him down and attacked him for no other reason than you wanted trouble".
The judge said: "You hit him time and time again until he was unconscious. This was a sustained, savage and senseless attack.
"You dragged his motionless body into the street and left him there to die. You showed no remorse then and you have shown no remorse since."
Members of Pte Boyd's family were not in court today for the sentencing.
They have returned to Gibraltar where they live, but victim impact statements were read out during the sentencing.
His mother Michelle Rogers said: "His life was taken in the blink of an eye. My son will not knock at my door again. There are times I text or call his mobile. I cry every night before I sleep, if I sleep. How can I explain the pain in my heart?
"It is unbearable, he has taken my son's life and destroyed our family."
His stepfather Jeremy Rogers said: "I don't want the pain to go away because if the pain goes away, so will Matthew."
Exeter Chiefs pair Byron McGuigan and Chrysander Botha will leave Sandy Park in the summer, the club has confirmed.
[NEXT_CONCEPT]
A Brecon man who murdered a soldier in the town has been sentenced to life with a minimum of 16 years in prison.