Since there are daily posts like "Will I be able to get the mythic if I'm at this many sigils?" I decided to do some calculations
Read the conclusion if you don't want to read all this and If anything is wrong here please feel free to correct me in the comments.
I'll be taking a weekly total of 44 sigils which is all the sigil tasks excluding the friend teamup tasks and the daily login and the redemption code.
Now, we have 59 days left and the new weekly tasks arrived 2 days ago so 61 days.
61/7 = 8.7 weeks, we take 8 weeks since the 9th week won't start because the event will end.
8x44 = 352 sigils that are left to be taken if you only do the weekly tasks
Since we get daily login sigils which vary from 1-5 I'll take the minimum of 1 per day, so,
8x7 = 56 minimum sigils left if you get 1 each day which you 100% won't because you can also get more sigils and this is just the minimum.
352+56 = 408 sigils if you add the daily login sigils
If you also include the friend teamup tasks which gives a total of 7 sigils per week then you get
8x7 = 56 sigils just from the friend teamup tasks
408+56 = 464 sigils if you also include the friend teamup tasks.
If you haven't used the 25 sigil redemption code ( "FREEMYTHICEVENT") then you would have 464+25 = 489 sigils starting now
Conclusion: If you have at least 36 sigils and do every task and get a minimum of 1 sigil per day from the daily login then you can get the free mythic as you would get 464 sigils if you start this week and an extra 25 if you haven't redeemed the redemption code.